arm64: dts: mediatek: mt6795: Add cpu-map and L2 cache

This SoC is HMP and has two clusters with four Cortex-A53 cores each:
declare a cpu map and, while at it, also add the next-level-cache
properties.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20220609112303.117928-3-angelogioacchino.delregno@collabora.com


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