block: gendisk integrity wrapper

This is a wrapper for accessing a gendisk's integrity bits.  It allows
the integrity support in MD to be compiled with BLK_DEV_INTEGRITY off.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

---

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -962,6 +962,11 @@ static inline struct blk_integrity *bdev
 	return bdev->bd_disk->integrity;
 }
 
+static inline struct blk_integrity *blk_get_integrity(struct gendisk *disk)
+{
+	return disk->integrity;
+}
+
 static inline unsigned int bdev_get_tag_size(struct block_device *bdev)
 {
 	struct blk_integrity *bi = bdev_get_integrity(bdev);
@@ -1004,6 +1009,7 @@ static inline int blk_integrity_rq(struc
 #define blk_rq_count_integrity_sg(a)		(0)
 #define blk_rq_map_integrity_sg(a, b)		(0)
 #define bdev_get_integrity(a)			(0)
+#define blk_get_integrity(a)			(0)
 #define bdev_get_tag_size(a)			(0)
 #define blk_integrity_compare(a, b)		(0)
 #define blk_integrity_register(a, b)		(0)