arm64: dts: Add MediaTek MT8186 dts and evaluation board and Makefile

MT8186 is a SoC based on 64bit ARMv8 architecture. It contains 6 CA55
and 2 CA76 cores. MT8186 share many HW IP with MT65xx series.

We add basic chip support for MediaTek MT8186 on evaluation board.

Signed-off-by: Allen-KH Cheng <Allen-KH.Cheng@mediatek.com>
Link: https://lore.kernel.org/r/20220825170448.17024-1-allen-kh.cheng@mediatek.com


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