arm64: dts: librem5-devkit: add the regulators for DVFS

Specify which regulator is used for cpufreq DVFS.
Signed-off-by: Angus Ainslie (Purism) <angus@akkea.ca>
Signed-off-by: Martin Kepplinger <martin.kepplinger@puri.sm>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mq-librem5-devkit.dts

@@ -227,6 +227,22 @@ wifi_pwr_en: regulator-wifi-en {
 	};
 };
 
+&A53_0 {
+	cpu-supply = <&buck2_reg>;
+};
+
+&A53_1 {
+	cpu-supply = <&buck2_reg>;
+};
+
+&A53_2 {
+	cpu-supply = <&buck2_reg>;
+};
+
+&A53_3 {
+	cpu-supply = <&buck2_reg>;
+};
+
 &clk {
 	assigned-clocks = <&clk IMX8MQ_AUDIO_PLL1>, <&clk IMX8MQ_AUDIO_PLL2>;
 	assigned-clock-rates = <786432000>, <722534400>;