ARM: dts: imx51: ZII: Add missing phy-mode

The DSA framework has got more picky about always having a phy-mode
for the CPU port. The imx51 Ethernet supports MII, and RMII. Set the
switch phy-mode based on how the SoC Ethernet port has been
configured.

Additionally, the cpu label has never actually been used in the
binding, so remove it.
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx51-zii-rdu1.dts

@@ -181,7 +181,7 @@ ports {
 
 				port@0 {
 					reg = <0>;
-					label = "cpu";
+					phy-mode = "rev-mii";
 					ethernet = <&fec>;
 
 					fixed-link {

arch/arm/boot/dts/imx51-zii-scu2-mezz.dts

@@ -82,7 +82,7 @@ port@3 {
 
 				port@4 {
 					reg = <4>;
-					label = "cpu";
+					phy-mode = "rev-mii";
 					ethernet = <&fec>;
 
 					fixed-link {

arch/arm/boot/dts/imx51-zii-scu3-esb.dts

@@ -267,7 +267,6 @@ fixed-link {
 
 				port@6 {
 					reg = <6>;
-					label = "cpu";
 					phy-mode = "mii";
 					ethernet = <&fec>;