dt-bindings: arm: toshiba: Add the TMPV7708 RM main board

Add an entry for the Toshiba Visconti TMPV7708 RM main board
(tmpv7708-rm-mbrc) to the board/SoC bindings.
Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>
Reviewed-by: Punit Agrawal <punit1.agrawal@toshiba.co.jp>
Reviewed-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/arm/toshiba.yaml

@@ -16,5 +16,7 @@ properties:
     oneOf:
       - description: Visconti5 TMPV7708
         items:
+          - enum:
+              - toshiba,tmpv7708-rm-mbrc  # TMPV7708 RM main board
           - const: toshiba,tmpv7708
 ...