ramips: mt7628: update dts for upstream gpio-mt7621 driver

ramips: mt7628: update dts for upstream gpio-mt7621 driver

upstream driver merged 3 separated gpio banks into one gpio node.
and gpioX Y in our local driver should be replaced with gpio X*32+Y.

This patch is created using the following sed command:
sed -i -r 's/(.*)gpio([0-9]) ([0-9]+)(.*)/echo "\1gpio $((\2*32+\3))\4"/ge'

Signed-off-by: Chuanhong Guo <gch981213@gmail.com>