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 <[e-mail]>
Acked-by: Rob Herring (Arm) <[e-mail]>
Reviewed-by: Geert Uytterhoeven <[e-mail]>
Link: https://lore.kernel.org/[e-mail]
Signed-off-by: Geert Uytterhoeven <[e-mail]>

Documentation/devicetree/bindings/power/renesas,rcar-sysc.yaml

···
       - renesas,r8a7745-sysc  # RZ/G1E
       - renesas,r8a77470-sysc # RZ/G1C
       - renesas,r8a774a1-sysc # RZ/G2M
+      - renesas,r8a774a3-sysc # RZ/G2M v3.0
       - renesas,r8a774b1-sysc # RZ/G2N
       - renesas,r8a774c0-sysc # RZ/G2E
       - renesas,r8a774e1-sysc # RZ/G2H