xfs: fix unreferenced var error in xfs_buf.c

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Alex Elder <aelder@sgi.com>

fs/xfs/linux-2.6/xfs_buf.c

@@ -657,8 +657,6 @@ xfs_buf_readahead(
 	xfs_off_t		ioff,
 	size_t			isize)
 {
-	struct backing_dev_info *bdi;
-
 	if (bdi_read_congested(target->bt_bdi))
 		return;