pinctrl: sh-pfc: Use dev_notice_once() instead of open-coding

At the time of commit 9a643c9a ("sh-pfc: Convert message
printing from pr_* to dev_*"), the dev_*_once() variants didn't exist
yet, so the once behavior was open-coded.

Since commit e135303b ("device: Add dev_<level>_once variants")
they do, so "revert" to the good practice of using a helper.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Ulrich Hecht <uli+renesas@fpond.eu>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>

drivers/pinctrl/sh-pfc/gpio.c

@@ -255,18 +255,13 @@ static int gpio_pin_setup(struct sh_pfc_chip *chip)
 #ifdef CONFIG_PINCTRL_SH_FUNC_GPIO
 static int gpio_function_request(struct gpio_chip *gc, unsigned offset)
 {
-	static bool __print_once;
 	struct sh_pfc *pfc = gpio_to_pfc(gc);
 	unsigned int mark = pfc->info->func_gpios[offset].enum_id;
 	unsigned long flags;
 	int ret;
 
-	if (!__print_once) {
-		dev_notice(pfc->dev,
-			   "Use of GPIO API for function requests is deprecated."
-			   " Convert to pinctrl\n");
-		__print_once = true;
-	}
+	dev_notice_once(pfc->dev,
+			"Use of GPIO API for function requests is deprecated, convert to pinctrl\n");
 
 	if (mark == 0)
 		return -EINVAL;