xfs: mark the record passed into xchk_btree functions as const

xchk_btree calls a user-supplied function to validate each btree record
that it finds.  Those functions are not supposed to change the record
data, so mark the parameter const.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/scrub/rmap.c

@@ -88,7 +88,7 @@ xchk_rmapbt_xref(
 STATIC int
 xchk_rmapbt_rec(
 	struct xchk_btree	*bs,
-	union xfs_btree_rec	*rec)
+	const union xfs_btree_rec *rec)
 {
 	struct xfs_mount	*mp = bs->cur->bc_mp;
 	struct xfs_rmap_irec	irec;