block: Consolidate duplicated bio_trim() implementations

Someone cut and pasted md's md_trim_bio() into xen-blkfront.c. Come on,
we should know better than this.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Neil Brown <neilb@suse.de>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index aacf6bf..af6681b1 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1097,8 +1097,8 @@
 		r1_bio->read_disk = rdisk;
 
 		read_bio = bio_clone_mddev(bio, GFP_NOIO, mddev);
-		md_trim_bio(read_bio, r1_bio->sector - bio->bi_sector,
-			    max_sectors);
+		bio_trim(read_bio, r1_bio->sector - bio->bi_sector,
+			 max_sectors);
 
 		r1_bio->bios[rdisk] = read_bio;
 
@@ -1266,7 +1266,7 @@
 			continue;
 
 		mbio = bio_clone_mddev(bio, GFP_NOIO, mddev);
-		md_trim_bio(mbio, r1_bio->sector - bio->bi_sector, max_sectors);
+		bio_trim(mbio, r1_bio->sector - bio->bi_sector, max_sectors);
 
 		if (first_clone) {
 			/* do behind I/O ?
@@ -2126,7 +2126,7 @@
 		wbio->bi_sector = r1_bio->sector;
 		wbio->bi_size = r1_bio->sectors << 9;
 
-		md_trim_bio(wbio, sector - r1_bio->sector, sectors);
+		bio_trim(wbio, sector - r1_bio->sector, sectors);
 		wbio->bi_sector += rdev->data_offset;
 		wbio->bi_bdev = rdev->bdev;
 		if (submit_bio_wait(WRITE, wbio) == 0)
@@ -2241,7 +2241,7 @@
 		}
 		r1_bio->read_disk = disk;
 		bio = bio_clone_mddev(r1_bio->master_bio, GFP_NOIO, mddev);
-		md_trim_bio(bio, r1_bio->sector - bio->bi_sector, max_sectors);
+		bio_trim(bio, r1_bio->sector - bio->bi_sector, max_sectors);
 		r1_bio->bios[r1_bio->read_disk] = bio;
 		rdev = conf->mirrors[disk].rdev;
 		printk_ratelimited(KERN_ERR