btrfs: use appropriate define for the fsid

Though BTRFS_FSID_SIZE and BTRFS_UUID_SIZE are of the same size, we
should use the matching constant for the fsid buffer.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index f49b94a..20c1ba1 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -1769,7 +1769,7 @@ static inline int scrub_check_fsid(u8 fsid[],
 	struct btrfs_fs_devices *fs_devices = spage->dev->fs_devices;
 	int ret;
 
-	ret = memcmp(fsid, fs_devices->fsid, BTRFS_UUID_SIZE);
+	ret = memcmp(fsid, fs_devices->fsid, BTRFS_FSID_SIZE);
 	return !ret;
 }