btrfs: Always pass 0 bio_offset for btree_submit_bio_start

The btree submit hook queues the async csum and forwards the bio_offset
parameter passed to btree_submit_bio_hook. This is redundant since
btree_submit_bio_start calls btree_csum_one_bio which doesn't use the
offset at all. No functional changes.
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/disk-io.c

@@ -913,8 +913,7 @@ static blk_status_t btree_submit_bio_hook(struct inode *inode, struct bio *bio,
 		 * checksumming can happen in parallel across all CPUs
 		 */
 		ret = btrfs_wq_submit_bio(fs_info, bio, mirror_num, 0,
-					  bio_offset, inode,
-					  btree_submit_bio_start);
+					  0, inode, btree_submit_bio_start);
 	}
 
 	if (ret)