arm64: dts: rockchip: Enable PCIe for Radxa Rock Pi 4 board

Radxa Rock Pi 4 is equipped with M.2 PCIe slot,
so enable PCIe for the board.

The changes has been tested with Intel SSD 660p series device.

    01:00.0 Class 0108: Device 8086:f1a8 (rev 03)
Signed-off-by: Matwey V. Kornilov <matwey@sai.msu.ru>
Link: https://lore.kernel.org/r/20191117101545.6406-1-matwey@sai.msu.ruSigned-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3399-rock-pi-4.dts

@@ -463,6 +463,20 @@ &pmu_io_domains {
 	pmu1830-supply = <&vcc_3v0>;
 };
 
+&pcie_phy {
+	status = "okay";
+};
+
+&pcie0 {
+	ep-gpios = <&gpio4 RK_PD3 GPIO_ACTIVE_HIGH>;
+	max-link-speed = <2>;
+	num-lanes = <4>;
+	pinctrl-0 = <&pcie_clkreqnb_cpm>;
+	pinctrl-names = "default";
+	vpcie3v3-supply = <&vcc3v3_pcie>;
+	status = "okay";
+};
+
 &pinctrl {
 	bt {
 		bt_enable_h: bt-enable-h {