Compiler is not happy:

  regcache.c:410:9: warning: Using plain integer as NULL pointer

Replace integer 0 by NULL.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 drivers/base/regmap/regcache.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/base/regmap/regcache.c b/drivers/base/regmap/regcache.c
index 2e41cb12b8e2..bd7462c54271 100644
--- a/drivers/base/regmap/regcache.c
+++ b/drivers/base/regmap/regcache.c
@@ -407,7 +407,7 @@ int regcache_sync(struct regmap *map)
 	 * have gone out of sync, force writes of all the paging
 	 * registers.
 	 */
-	rb_for_each(node, 0, &map->range_tree, rbtree_all) {
+	rb_for_each(node, NULL, &map->range_tree, rbtree_all) {
 		struct regmap_range_node *this =
 			rb_entry(node, struct regmap_range_node, node);
 
-- 
2.43.0.rc1.1336.g36b5255a03ac