arm64: dts: mediatek: mt6795: Add Cortex A53 PMU nodes

Add the required nodes to enable the PMU on this SoC.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20220609112303.117928-4-angelogioacchino.delregno@collabora.com


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