Documentation: DT: Add entry for Freescale LS1043a-RDB board

Signed-off-by: Mingkai Hu <Mingkai.Hu@freescale.com>
Signed-off-by: Hou Zhiqiang <B48286@freescale.com>
Signed-off-by: Li Yang <leoli@freescale.com>
Signed-off-by: Olof Johansson <olof@lixom.net>

Documentation/devicetree/bindings/arm/fsl.txt

@@ -131,6 +131,10 @@ Example:
 Freescale ARMv8 based Layerscape SoC family Device Tree Bindings
 ----------------------------------------------------------------
 
+LS1043A ARMv8 based RDB Board
+Required root node properties:
+    - compatible = "fsl,ls1043a-rdb", "fsl,ls1043a";
+
 LS2080A ARMv8 based Simulator model
 Required root node properties:
     - compatible = "fsl,ls2080a-simu", "fsl,ls2080a";