mips: dts: remove label = "cpu" from DSA dt-binding

This is not used by the DSA dt-binding, so remove it from all devicetrees.
Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Acked-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Reviewed-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/boot/dts/qca/ar9331.dtsi

@@ -176,7 +176,6 @@ ports {
 
 						switch_port0: port@0 {
 							reg = <0x0>;
-							label = "cpu";
 							ethernet = <&eth1>;
 
 							phy-mode = "gmii";

arch/mips/boot/dts/ralink/mt7621.dtsi

@@ -386,7 +386,6 @@ port@4 {
 
 					port@6 {
 						reg = <6>;
-						label = "cpu";
 						ethernet = <&gmac0>;
 						phy-mode = "trgmii";