[S390] remove tape block docu

After git commit 66ceed5a removed
the tape block device driver, remove its documentation as well.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

Documentation/s390/TAPE

-Channel attached Tape device driver 
-
------------------------------WARNING-----------------------------------------
-This driver is considered to be EXPERIMENTAL. Do NOT use it in 
-production environments. Feel free to test it and report problems back to us. 
------------------------------------------------------------------------------
-
-The LINUX for zSeries tape device driver manages channel attached tape drives 
-which are compatible to IBM 3480 or IBM 3490 magnetic tape subsystems. This 
-includes various models of these devices (for example the 3490E). 
-
-
-Tape driver features 
-
-The device driver supports a maximum of 128 tape devices. 
-No official LINUX device major number is assigned to the zSeries tape device 
-driver. It allocates major numbers dynamically and reports them on system 
-startup. 
-Typically it will get major number 254 for both the character device front-end 
-and the block device front-end. 
-
-The tape device driver needs no kernel parameters. All supported devices 
-present are detected on driver initialization at system startup or module load.
-The devices detected are ordered by their subchannel numbers. The device with 
-the lowest subchannel number becomes device 0, the next one will be device 1 
-and so on. 
-
-
-Tape character device front-end 
-
-The usual way to read or write to the tape device is through the character 
-device front-end. The zSeries tape device driver provides two character devices
-for each physical device -- the first of these will rewind automatically when 
-it is closed, the second will not rewind automatically. 
-
-The character device nodes are named /dev/rtibm0 (rewinding) and /dev/ntibm0 
-(non-rewinding) for the first device, /dev/rtibm1 and /dev/ntibm1 for the 
-second, and so on. 
-
-The character device front-end can be used as any other LINUX tape device. You 
-can write to it and read from it using LINUX facilities such as GNU tar. The 
-tool mt can be used to perform control operations, such as rewinding the tape 
-or skipping a file. 
-
-Most LINUX tape software should work with either tape character device. 
-
-
-Tape block device front-end 
-
-The tape device may also be accessed as a block device in read-only mode. 
-This could be used for software installation in the same way as it is used with 
-other operation systems on the zSeries platform (and most LINUX 
-distributions are shipped on compact disk using ISO9660 filesystems). 
-
-One block device node is provided for each physical device. These are named 
-/dev/btibm0 for the first device, /dev/btibm1 for the second and so on. 
-You should only use the ISO9660 filesystem on LINUX for zSeries tapes because 
-the physical tape devices cannot perform fast seeks and the ISO9660 system is 
-optimized for this situation. 
-
-
-Tape block device example 
-
-In this example a tape with an ISO9660 filesystem is created using the first 
-tape device. ISO9660 filesystem support must be built into your system kernel
-for this. 
-The mt command is used to issue tape commands and the mkisofs command to 
-create an ISO9660 filesystem: 
-
-- create a LINUX directory (somedir) with the contents of the filesystem 
-     mkdir somedir
-     cp contents somedir 
-
-- insert a tape 
-
-- ensure the tape is at the beginning 
-     mt -f /dev/ntibm0 rewind 
-
-- set the blocksize of the character driver. The blocksize 2048 bytes
-  is commonly used on ISO9660 CD-Roms
-     mt -f /dev/ntibm0 setblk 2048 
-
-- write the filesystem to the character device driver 
-     mkisofs -o /dev/ntibm0 somedir 
-
-- rewind the tape again 
-     mt -f /dev/ntibm0 rewind 
-
-- Now you can mount your new filesystem as a block device: 
-     mount -t iso9660 -o ro,block=2048 /dev/btibm0 /mnt 
-
-TODO List 
-
-   - Driver has to be stabilized still
-
-BUGS 
-
-This driver is considered BETA, which means some weaknesses may still
-be in it.
-If an error occurs which cannot be handled by the code you will get a 
-sense-data dump.In that case please do the following: 
-
-1. set the tape driver debug level to maximum: 
-     echo 6 >/proc/s390dbf/tape/level 
-
-2. re-perform the actions which produced the bug. (Hopefully the bug will 
-   reappear.) 
-
-3. get a snapshot from the debug-feature: 
-     cat /proc/s390dbf/tape/hex_ascii >somefile 
-
-4. Now put the snapshot together with a detailed description of the situation 
-   that led to the bug: 
- - Which tool did you use? 
- - Which hardware do you have? 
- - Was your tape unit online? 
- - Is it a shared tape unit? 
-
-5. Send an email with your bug report to: 
-     mailto:Linux390@de.ibm.com 
-
-