include/linux/bio.h: use a static inline function for bio_integrity_clone()

When CONFIG_BLK_DEV_INTEGRITY is not set, we get these warnings:

drivers/md/dm.c: In function 'split_bvec':
drivers/md/dm.c:1061:3: warning: statement with no effect
drivers/md/dm.c: In function 'clone_bio':
drivers/md/dm.c:1088:3: warning: statement with no effect
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/bio.h

@@ -519,7 +519,11 @@ extern void bio_integrity_init(void);
 #define bioset_integrity_create(a, b)	(0)
 #define bio_integrity_prep(a)		(0)
 #define bio_integrity_enabled(a)	(0)
-#define bio_integrity_clone(a, b, c, d)	(0)
+static inline int bio_integrity_clone(struct bio *bio, struct bio *bio_src,
+				      gfp_t gfp_mask, struct bio_set *bs)
+{
+	return 0;
+}
 #define bioset_integrity_free(a)	do { } while (0)
 #define bio_integrity_free(a, b)	do { } while (0)
 #define bio_integrity_endio(a, b)	do { } while (0)