pinctrl: mt7622: mark expected switch fall-through

In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.

Warning level 2 was used: -Wimplicit-fallthrough=2

Addresses-Coverity-ID: 1463284 ("Missing break in switch")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/mediatek/pinctrl-mt7622.c

@@ -1263,6 +1263,7 @@ static int mtk_pinconf_set(struct pinctrl_dev *pctldev, unsigned int pin,
 					       MTK_DISABLE);
 			if (err)
 				goto err;
+			/* else: fall through */
 		case PIN_CONFIG_INPUT_ENABLE:
 		case PIN_CONFIG_SLEW_RATE:
 			reg = (param == PIN_CONFIG_SLEW_RATE) ?