net: mediatek: remove superfluous pin setup for MT7622 SoC

Remove superfluous pin setup to get out of accessing invalid I/O pin
registers because the way for pin configuring tends to be different from
various SoCs and thus it should be better being managed and controlled by
the pinctrl driver which MT7622 already can support.

Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>