arm64: dts: renesas: r8a779a0: Add RWDT node

Add a device node for the Watchdog Timer (WDT) controller on the
R8A779A0 SoC.

Signed-off-by: Hoang Vo <hoang.vo.eb@renesas.com>
[wsa: rebased to mainline]
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/20201218173731.12839-4-wsa+renesas@sang-engineering.com


Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>