dt-bindings: power: rcar-sysc: Document r8a774b1 sysc

Document bindings for the RZ/G2N (a.k.a. R8A774B1) system controller.
Signed-off-by: Biju Das <biju.das@bp.renesas.com>
Link: https://lore.kernel.org/r/1568881036-4404-2-git-send-email-biju.das@bp.renesas.comSigned-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

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

@@ -12,6 +12,7 @@ Required properties:
       - "renesas,r8a7745-sysc" (RZ/G1E)
       - "renesas,r8a77470-sysc" (RZ/G1C)
       - "renesas,r8a774a1-sysc" (RZ/G2M)
+      - "renesas,r8a774b1-sysc" (RZ/G2N)
       - "renesas,r8a774c0-sysc" (RZ/G2E)
       - "renesas,r8a7779-sysc" (R-Car H1)
       - "renesas,r8a7790-sysc" (R-Car H2)