dt-bindings: arm: fsl: add i.MX28 Amarula rmm board

The board includes the following resources:
 - 256 Mbytes NAND Flash
 - 128 Mbytes DRAM DDR2
 - CAN
 - USB 2.0 high-speed/full-speed
 - Ethernet MAC

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

@@ -89,6 +89,7 @@ properties:
       - description: i.MX28 based Boards
         items:
           - enum:
+              - amarula,imx28-rmm
               - armadeus,imx28-apf28      # APF28 SoM
               - bluegiga,apx4devkit       # Bluegiga APx4 SoM on dev board
               - crystalfontz,cfa10036     # Crystalfontz CFA-10036 SoM