pinctrl: mt7622: fix that pinctrl_claim_hogs cannot work

To allow claiming hogs by pinctrl, we cannot enable pinctrl until all
groups and functions are being added done. Also, it's necessary that
the corresponding gpiochip is being added when the pinctrl device is
enabled.

Cc: stable@vger.kernel.org
Fixes: d6ed9355 ("pinctrl: mediatek: add pinctrl driver for MT7622 SoC")
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>