arm64: dts: meson: odroid-c2: p5v0 is the main 5V power input

As per the schematic Monolithic Power Systems MP2161GJ-C499
supply a fixed output voltage of 5.0V. This supplies linked
to VDD_EE, HDMI_P5V0, USB_POWER, VCCK, VDDIO_AO1V8, VDDIO_AO3V3,
VDD3V3, DDR3_1V5 according to the schematics.

Cc: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Cc: Jerome Brunet <jbrunet@baylibre.com>
Cc: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Anand Moon <linux.amoon@gmail.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>

arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts

@@ -50,6 +50,15 @@ blue {
 		};
 	};
 
+	p5v0: regulator-p5v0 {
+		compatible = "regulator-fixed";
+
+		regulator-name = "P5V0";
+		regulator-min-microvolt = <5000000>;
+		regulator-max-microvolt = <5000000>;
+		regulator-always-on;
+	};
+
 	tflash_vdd: regulator-tflash_vdd {
 		/*
 		 * signal name from schematics: TFLASH_VDD_EN