arm64: dts: add dts nodes for MT6779

this adds initial MT6779 dts settings for board support,
including cpu, gic, timer, ccf, pinctrl, uart, sysirq...etc.

Signed-off-by: Hanks Chen <hanks.chen@mediatek.com>
Link: https://lore.kernel.org/r/1596115816-11758-3-git-send-email-hanks.chen@mediatek.com


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