dt-bindings: arm: fsl: support Engicam MicroGEA RMM board

Add devicetree bindings for Engicam MicroGEA RMM board based on the
Engicam MicroGEA SoM (System-on-Module).

Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

Author: passgat

Documentation/devicetree/bindings/arm/fsl.yaml

@@ -774,6 +774,7 @@ properties:
         items:
           - enum:
               - engicam,microgea-imx6ull-bmm       # i.MX6ULL Engicam MicroGEA BMM Board
+              - engicam,microgea-imx6ull-rmm       # i.MX6ULL Engicam MicroGEA RMM Board
           - const: engicam,microgea-imx6ull        # i.MX6ULL Engicam MicroGEA SoM
           - const: fsl,imx6ull