xfs: make the record pointer passed to query_range functions const

The query_range functions are supposed to call a caller-supplied
function on each record found in the dataset.  These functions don't
own the memory storing the record, so don't let them change the record.

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

fs/xfs/libxfs/xfs_alloc.c

@@ -3392,7 +3392,7 @@ struct xfs_alloc_query_range_info {
 STATIC int
 xfs_alloc_query_range_helper(
 	struct xfs_btree_cur		*cur,
-	union xfs_btree_rec		*rec,
+	const union xfs_btree_rec	*rec,
 	void				*priv)
 {
 	struct xfs_alloc_query_range_info	*query = priv;