xfs: fix error initialization

Eric Sandeen reported a gcc complaint about uninitialized error
variables, so fix that.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reported-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/xfs_reflink.c

@@ -1437,7 +1437,7 @@ xfs_reflink_dirty_extents(
 	xfs_off_t		flen;
 	struct xfs_bmbt_irec	map[2];
 	int			nmaps;
-	int			error;
+	int			error = 0;
 
 	while (end - fbno > 0) {
 		nmaps = 1;