pinctrl: renesas: rcar: Do not enforce GPIO if already muxed

For Renesas PFCs not setting .strict, we can snoop GPIOs which are
already muxed to some other function.  To actually make use of that, we
shouldn't mux them back to GPIO if they have been already muxed to
something.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/20211210113226.40111-1-wsa+renesas@sang-engineering.comSigned-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

drivers/pinctrl/renesas/pinctrl.c

@@ -397,7 +397,7 @@ static int sh_pfc_gpio_request_enable(struct pinctrl_dev *pctldev,
 
 	spin_lock_irqsave(&pfc->lock, flags);
 
-	if (!pfc->gpio) {
+	if (!pfc->gpio && !cfg->mux_mark) {
 		/* If GPIOs are handled externally the pin mux type needs to be
 		 * set to GPIO here.
 		 */