arm64: dts: renesas: Add Renesas R-Car X5H R8A78000 SoC DTs

arm64: dts: renesas: Add Renesas R-Car X5H R8A78000 SoC DTs

Add initial device trees for Renesas R-Car X5H R8A78000 SoC.
Include very basic clock, reset, power domain headers which
are used to control supported peripherals via SCMI / SCP. The
headers are currently kept limited to avoid possible ABI break.
A lot of clock are still stubbed via fixed-clock, this is going
to be gradually removed over time, as more of the platform is
upstreamed.

Signed-off-by: Hai Pham <hai.pham.ud@renesas.com>
Signed-off-by: Khanh Le <khanh.le.xr@renesas.com>
Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>