regulator: of: Make regulator_of_get_init_node static

Fix sparse warning:

drivers/regulator/of_regulator.c:374:20:
 warning: symbol 'regulator_of_get_init_node' was not declared. Should it be static?
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/of_regulator.c

@@ -371,8 +371,9 @@ int of_regulator_match(struct device *dev, struct device_node *node,
 }
 EXPORT_SYMBOL_GPL(of_regulator_match);
 
-struct device_node *regulator_of_get_init_node(struct device *dev,
-					       const struct regulator_desc *desc)
+static struct
+device_node *regulator_of_get_init_node(struct device *dev,
+					const struct regulator_desc *desc)
 {
 	struct device_node *search, *child;
 	const char *name;