scsi: dm: Remove WRITE_SAME support

There are no more end-users of REQ_OP_WRITE_SAME left, so we can start
deleting it.

Link: https://lore.kernel.org/r/20220209082828.2629273-7-hch@lst.de


Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>