cpumask: replace node_to_cpumask with cpumask_of_node.

Impact: cleanup

node_to_cpumask (and the blecherous node_to_cpumask_ptr which
contained a declaration) are replaced now everyone implements
cpumask_of_node.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/mm/quicklist.c b/mm/quicklist.c
index 8dbb680..e66d07d 100644
--- a/mm/quicklist.c
+++ b/mm/quicklist.c
@@ -29,7 +29,7 @@
 	int node = numa_node_id();
 	struct zone *zones = NODE_DATA(node)->node_zones;
 	int num_cpus_on_node;
-	node_to_cpumask_ptr(cpumask_on_node, node);
+	const struct cpumask *cpumask_on_node = cpumask_of_node(node);
 
 	node_free_pages =
 #ifdef CONFIG_ZONE_DMA