ARM: dts: Add devicetree compatibles for LS1021A based boards

Add missing devicetree compatibles for the following LS1021A based
boards:

ls1021a-moxa-uc-8410a.dts
ls1021a-qds.dts
ls1021a-twr.dts
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/ls1021a-moxa-uc-8410a.dts

@@ -18,6 +18,7 @@
 
 / {
 	model = "Moxa UC-8410A";
+	compatible = "fsl,ls1021a-moxa-uc-8410a", "fsl,ls1021a";
 
 	aliases {
 		enet0_rgmii_phy = &rgmii_phy0;

arch/arm/boot/dts/ls1021a-qds.dts

@@ -51,6 +51,7 @@
 
 / {
 	model = "LS1021A QDS Board";
+	compatible = "fsl,ls1021a-qds", "fsl,ls1021a";
 
 	aliases {
 		enet0_rgmii_phy = &rgmii_phy1;

arch/arm/boot/dts/ls1021a-twr.dts

@@ -51,6 +51,7 @@
 
 / {
 	model = "LS1021A TWR Board";
+	compatible = "fsl,ls1021a-twr", "fsl,ls1021a";
 
 	aliases {
 		enet2_rgmii_phy = &rgmii_phy1;