block: Get rid of bdev_integrity_enabled()

bdev_integrity_enabled() is only used by bio_integrity_enabled().
Combine these two functions.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --cc Documentation/block/data-integrity.txt
Simple merge

diff --cc block/bio-integrity.c
Simple merge

diff --cc include/linux/bio.h
Simple merge