dt-bindings: memory: renesas,rpc-if: Add optional interrupts property

For completeness add optional interrupts property.
Signed-off-by: NLad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: NBiju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: NWolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: NRob Herring <robh@kernel.org>
Reviewed-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20211025205631.21151-3-prabhakar.mahadev-lad.rj@bp.renesas.comSigned-off-by: NKrzysztof Kozlowski <krzysztof.kozlowski@canonical.com>

Documentation/devicetree/bindings/memory-controllers/renesas,rpc-if.yaml

@@ -56,6 +56,9 @@ properties:
 
   clocks: true
 
+  interrupts:
+    maxItems: 1
+
   power-domains:
     maxItems: 1