arm64: dts: mt6358: add mt6358-keys node

This enables the power,home keys on MediaTek boards with a mt6358 pmic.

Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Link: https://lore.kernel.org/r/20220121140323.4080640-5-mkorpershoek@baylibre.com


Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>