dt-bindings: power: rcar-sysc: Document r8a7744 SYSC binding

Add binding documentation for the RZ/G1N (R8A7744) SYSC block.
Signed-off-by: Biju Das <biju.das@bp.renesas.com>
Reviewed-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

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

@@ -8,6 +8,7 @@ and various coprocessors.
 Required properties:
   - compatible: Must contain exactly one of the following:
       - "renesas,r8a7743-sysc" (RZ/G1M)
+      - "renesas,r8a7744-sysc" (RZ/G1N)
       - "renesas,r8a7745-sysc" (RZ/G1E)
       - "renesas,r8a77470-sysc" (RZ/G1C)
       - "renesas,r8a774a1-sysc" (RZ/G2M)