check mtk_is_virt_gpio input parameter,
virtual gpio need to support eint mode.

add error handler for the ko case
to fix this boot fail:
pc : mtk_is_virt_gpio+0x20/0x38 [pinctrl_mtk_common_v2]
lr : mtk_gpio_get_direction+0x44/0xb0 [pinctrl_paris]

Fixes: edd54646 ("pinctrl: mediatek: avoid virtual gpio trying to set reg")
Signed-off-by: Hanks Chen <hanks.chen@mediatek.com>
Acked-by: Sean Wang <sean.wang@kernel.org>
Singed-off-by: Jie Yang <sin_jieyang@mediatek.com>
Link: https://lore.kernel.org/r/1597922546-29633-1-git-send-email-hanks.chen@mediatek.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>