ARM: dts: bcm2711: Add vmmc regulator in emmc2

The SD card power can be controlled trough a pin routed into the board's
external GPIO expander. Turn that into a regulator and provide it to
emmc2.

Signed-off-by: Nicolas Saenz Julienne <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

arch/arm/boot/dts/bcm2711-rpi-4-b.dts

···
 			  3300000 0x0>;
 		status = "okay";
 	};
+
+	sd_vcc_reg: sd_vcc_reg {
+		compatible = "regulator-fixed";
+		regulator-name = "vcc-sd";
+		regulator-min-microvolt = <3300000>;
+		regulator-max-microvolt = <3300000>;
+		regulator-boot-on;
+		enable-active-high;
+		gpio = <&expgpio 6 GPIO_ACTIVE_HIGH>;
+	};
 };
 
 &firmware {
···
 /* EMMC2 is used to drive the SD card */
 &emmc2 {
 	vqmmc-supply = <&sd_io_1v8_reg>;
+	vmmc-supply = <&sd_vcc_reg>;
 	broken-cd;
 	status = "okay";
 };