arm64: dts: mediatek: mt8395-genio-1200-evk: Add MT6359 PMIC key support

Add in mt8395-genio-1200-evk devicetree file a sub node in pmic for
the mt6359-keys compatible to add the Power and Home MT6359 PMIC keys
support.

Signed-off-by: Louis-Alexis Eyraud <louisalexis.eyraud@collabora.com>