dt-bindings: power: renesas: Document RZ/G2M v3.0 (r8a774a3) SYSC binding

dt-bindings: power: renesas: Document RZ/G2M v3.0 (r8a774a3) SYSC binding

Document bindings for the Renesas RZ/G2M v3.0 (a.k.a r8a774a3) SYSC block.
The RZ/G2M v3.0 SYSC is similar to the RZ/G2M v1.x SYSC however, it lacks
the A2VC power area. To handle this difference, introduce
renesas,r8a774a3-sysc compatible.

Signed-off-by: Oliver Rhodes <oliver.rhodes.aj@renesas.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/20240725100534.5374-3-oliver.rhodes.aj@renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>