arm64: dts: rockchip: enable NanoPC-T6 MiniPCIe power

The NanoPC-T6 has a Mini PCIe slot intended to be used for a 4G or LTE
modem. This slot has no PCIe functionality, only USB 2.0 pins are wired
to the SoC, and USIM pins are wired to a SIM card slot on the board.
Define the 3.3v supply for the slot so it can be used.
Signed-off-by: Hugh Cole-Baker <sigmaris@gmail.com>
Link: https://lore.kernel.org/r/20240109202729.54292-1-sigmaris@gmail.comSigned-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3588-nanopc-t6.dts

@@ -159,6 +159,18 @@ vcc3v3_pcie30: vcc3v3-pcie30-regulator {
 		regulator-max-microvolt = <3300000>;
 		vin-supply = <&vcc5v0_sys>;
 	};
+
+	vdd_4g_3v3: vdd-4g-3v3-regulator {
+		compatible = "regulator-fixed";
+		enable-active-high;
+		gpio = <&gpio4 RK_PC6 GPIO_ACTIVE_HIGH>;
+		pinctrl-names = "default";
+		pinctrl-0 = <&pin_4g_lte_pwren>;
+		regulator-name = "vdd_4g_3v3";
+		regulator-min-microvolt = <3300000>;
+		regulator-max-microvolt = <3300000>;
+		vin-supply = <&vcc5v0_sys>;
+	};
 };
 
 &combphy0_ps {
@@ -504,6 +516,10 @@ pcie_m2_1_pwren: pcie-m21-pwren {
 	};
 
 	usb {
+		pin_4g_lte_pwren: 4g-lte-pwren {
+			rockchip,pins = <4 RK_PC6 RK_FUNC_GPIO &pcfg_pull_none>;
+		};
+
 		typec5v_pwren: typec5v-pwren {
 			rockchip,pins = <1 RK_PD2 RK_FUNC_GPIO &pcfg_pull_none>;
 		};
@@ -884,6 +900,7 @@ &uart2 {
 };
 
 &u2phy2_host {
+	phy-supply = <&vdd_4g_3v3>;
 	status = "okay";
 };