pinctrl: mediatek: mtk-common: initialize unmask

cppcheck detected an uninitialized variable:

[drivers/pinctrl/mediatek/pinctrl-mtk-common.c:897]:
  (error) Uninitialized variable: unmask

unmask should be initialized to zero to ensure unmasking
only occurs if a previous mask occurred. The current situation
is that the unmask variable could contain any random garbage
causing random unexpected unmasking.
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/mediatek/pinctrl-mtk-common.c

@@ -881,6 +881,8 @@ static int mtk_gpio_set_debounce(struct gpio_chip *chip, unsigned offset,
 	if (!mtk_eint_get_mask(pctl, eint_num)) {
 		mtk_eint_mask(d);
 		unmask = 1;
+	} else {
+		unmask = 0;
 	}
 
 	clr_bit = 0xff << eint_offset;