dt-bindings: arm: renesas: Document RZ/A2M EVB

Add the RZ/A2M Evaluation board.
Signed-off-by: Chris Brandt <chris.brandt@renesas.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

Documentation/devicetree/bindings/arm/renesas.yaml

@@ -30,6 +30,8 @@ properties:
 
       - description: RZ/A2 (R7S9210)
         items:
+          - enum:
+              - renesas,rza2mevb # RZ/A2M Eval Board (RTK7921053S00000BE)
           - const: renesas,r7s9210
 
       - description: SH-Mobile AG5 (R8A73A00/SH73A0)