arm64: dts: renesas: ulcb: Add cpu-supply property to a57_0 node

Add the cpu-supply property to the a57_0 node, so Dynamic Voltage and
Frequency Scaling (DVFS) can change the CPU core voltage.
Signed-off-by: Yusuke Goda <yusuke.goda.sx@renesas.com>
Signed-off-by: Takeshi Kihara <takeshi.kihara.df@renesas.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20210326105009.1574424-3-geert+renesas@glider.be

arch/arm64/boot/dts/renesas/ulcb.dtsi

@@ -138,6 +138,10 @@ x23_clk: x23-clock {
 	};
 };
 
+&a57_0 {
+	cpu-supply = <&dvfs>;
+};
+
 &audio_clk_a {
 	clock-frequency = <22579200>;
 };