dt-bindings: irqchip: renesas-irqc: Document r8a774a1 support

Document RZ/G2M (R8A774A1) SoC bindings.
Reviewed-by: Biju Das <biju.das@bp.renesas.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

Documentation/devicetree/bindings/interrupt-controller/renesas,irqc.txt

@@ -12,6 +12,7 @@ Required properties:
     - "renesas,irqc-r8a7792" (R-Car V2H)
     - "renesas,irqc-r8a7793" (R-Car M2-N)
     - "renesas,irqc-r8a7794" (R-Car E2)
+    - "renesas,intc-ex-r8a774a1" (RZ/G2M)
     - "renesas,intc-ex-r8a7795" (R-Car H3)
     - "renesas,intc-ex-r8a7796" (R-Car M3-W)
     - "renesas,intc-ex-r8a77965" (R-Car M3-N)