arm64: Add DTS overlays for A64

• sun50i-a64-sid.dtso registers the Security ID node, needed for thermal
• sun50i-a64-ths.dtso registers the thermal node, for which we already have a

driver

• sun50i-a64-timer.dtso registers the timer node, needed as the generic timer glitch on A64 SoC.

Approved by: re (gjb)