ARM: dts: imx7d: correct cpu supply name for voltage scaling

Correct CPU supply name to meet cpufreq-dt driver's
requirement for voltage scaling.
Signed-off-by: NAnson Huang <Anson.Huang@nxp.com>
Reviewed-by: NFabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: NShawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx7d-cl-som-imx7.dts

@@ -33,7 +33,7 @@
 };
 
 &cpu0 {
-	arm-supply = <&sw1a_reg>;
+	cpu-supply = <&sw1a_reg>;
 };
 
 &fec1 {

arch/arm/boot/dts/imx7d-nitrogen7.dts

@@ -144,7 +144,7 @@
 };
 
 &cpu0 {
-	arm-supply = <&sw1a_reg>;
+	cpu-supply = <&sw1a_reg>;
 };
 
 &fec1 {

arch/arm/boot/dts/imx7d-sdb.dts

@@ -141,7 +141,7 @@
 };
 
 &cpu0 {
-	arm-supply = <&sw1a_reg>;
+	cpu-supply = <&sw1a_reg>;
 };
 
 &ecspi3 {