Fix the following build failure:

In file included from drivers/pinctrl/mediatek/pinctrl-mt8135.c:24:0:
drivers/pinctrl/mediatek/pinctrl-mtk-mt8135.h:19:32: fatal error:
	pinctrl-mtk-common.h: No such file or directory

seen when building arm:multi_v7_defconfig.

Fixes: 94097d89c145 ("pinctrl: mediatek: Add Pinctrl/GPIO driver for mt8135.")
Cc: Hongzhou Yang <hongzhou.yang@mediatek.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>