Rework of tape driver

  Almost complete rewrite of the s390 tape driver code by
  Martin Schwidefsky. Skipping the 2.4 era, this makes the tape
  code ready for the future.

  This driver probably doesn't have to change much before 2.6.

Authors:
	Martin Schwidefsky <schwidefsky@de.ibm.com>
	Stefan Bader <shbader@de.ibm.com>