dt-bindings: soc: renesas: Add RZ/V2M PWC

The Renesas RZ/V2M External Power Sequence Controller (PWC) IP
is capable of:
* external power supply on/off sequence generation
* on/off signal generation for the LPDDR4 core power supply (LPVDD)
* key input signals processing
* general-purpose output pins

Add the corresponding dt-bindings.

Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20230106125816.10600-2-fabrizio.castro.jz@renesas.com


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