bcachefs: Fix keylist size in btree_update

This fixes a buffer overrun, fortunately caught by a BUG_ON().
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/btree_update_interior.h

@@ -82,12 +82,12 @@ struct btree_update {
 	/* Nodes being freed: */
 	struct keylist			old_keys;
 	u64				_old_keys[BTREE_UPDATE_NODES_MAX *
-						  BKEY_BTREE_PTR_VAL_U64s_MAX];
+						  BKEY_BTREE_PTR_U64s_MAX];
 
 	/* Nodes being added: */
 	struct keylist			new_keys;
 	u64				_new_keys[BTREE_UPDATE_NODES_MAX *
-						  BKEY_BTREE_PTR_VAL_U64s_MAX];
+						  BKEY_BTREE_PTR_U64s_MAX];
 
 	/* New nodes, that will be made reachable by this update: */
 	struct btree			*new_nodes[BTREE_UPDATE_NODES_MAX];