powerpc: Fix warnings for arch/powerpc/mm/numa.c

Simple fixes for sparse warnings in this file.

Resolves:
arch/powerpc/mm/numa.c:198:24:
        warning: Using plain integer as NULL pointer

arch/powerpc/mm/numa.c:1157:5:
       warning: symbol 'hot_add_node_scn_to_nid' was not declared.
                Should it be static?

arch/powerpc/mm/numa.c:1238:28:
       warning: Using plain integer as NULL pointer

arch/powerpc/mm/numa.c:1538:6:
       warning: symbol 'topology_schedule_update' was not declared.
                Should it be static?
Signed-off-by: Robert C Jennings <rcj@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/mm/numa.c

@@ -195,7 +195,7 @@ static const __be32 *of_get_usable_memory(struct device_node *memory)
 	u32 len;
 	prop = of_get_property(memory, "linux,drconf-usable-memory", &len);
 	if (!prop || len < sizeof(unsigned int))
-		return 0;
+		return NULL;
 	return prop;
 }
 
@@ -1154,7 +1154,7 @@ static int hot_add_drconf_scn_to_nid(struct device_node *memory,
  * represented in the device tree as a node (i.e. memory@XXXX) for
  * each memblock.
  */
-int hot_add_node_scn_to_nid(unsigned long scn_addr)
+static int hot_add_node_scn_to_nid(unsigned long scn_addr)
 {
 	struct device_node *memory;
 	int nid = -1;
@@ -1235,7 +1235,7 @@ static u64 hot_add_drconf_memory_max(void)
         struct device_node *memory = NULL;
         unsigned int drconf_cell_cnt = 0;
         u64 lmb_size = 0;
-	const __be32 *dm = 0;
+	const __be32 *dm = NULL;
 
         memory = of_find_node_by_path("/ibm,dynamic-reconfiguration-memory");
         if (memory) {
@@ -1535,7 +1535,7 @@ static void topology_work_fn(struct work_struct *work)
 }
 static DECLARE_WORK(topology_work, topology_work_fn);
 
-void topology_schedule_update(void)
+static void topology_schedule_update(void)
 {
 	schedule_work(&topology_work);
 }