arm64: dts: mt7622: add pinctrl related device nodes

add pinctrl device nodes and rfb1 board, additionally include all pin
groups possible being used on rfb1 board and available gpio keys.

Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>