Last 3 users of kernel_scsi_ioctl() eliminated; two of them used to read
partition table by issuing a READ6 via ioctl (instead of just calling
scsi_bios_ptable() as every other ->biosparam() instance does).

The last one was doing a very quaint access to fields of scsi_device by
issuing SCSI_IOCLT_GET_LUN and then shuffling bits in the result.  Down
with that insanity...