pinctrl: core: Make pinctrl_init_controller() static

pinctrl_init_controller() is not used outside core.c, thus make it
static and prevent compiler to warn.

drivers/pinctrl/core.c:1943:21: warning: no previous prototype for ‘pinctrl_init_controller’ [-Wmissing-prototypes]
 struct pinctrl_dev *pinctrl_init_controller(struct pinctrl_desc *pctldesc,
                     ^~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/core.c

@@ -1939,9 +1939,9 @@ static int pinctrl_check_ops(struct pinctrl_dev *pctldev)
  * @dev: parent device for this pin controller
  * @driver_data: private pin controller data for this pin controller
  */
-struct pinctrl_dev *pinctrl_init_controller(struct pinctrl_desc *pctldesc,
-					    struct device *dev,
-					    void *driver_data)
+static struct pinctrl_dev *
+pinctrl_init_controller(struct pinctrl_desc *pctldesc, struct device *dev,
+			void *driver_data)
 {
 	struct pinctrl_dev *pctldev;
 	int ret;