arm64: tegra: Add support for PCIe endpoint mode in P2972-0000 platform

Add endpoint mode support for PCIe C5 controller in P2972-0000 platform
with information about supplies, PHY, PERST GPIO and GPIO that controls
PCIe reference clock coming from the host system.
Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

arch/arm64/boot/dts/nvidia/tegra194-p2972-0000.dts

@@ -199,6 +199,24 @@ pcie@141a0000 {
 			    "p2u-5", "p2u-6", "p2u-7";
 	};
 
+	pcie_ep@141a0000 {
+		status = "disabled";
+
+		vddio-pex-ctl-supply = <&vdd_1v8ao>;
+
+		reset-gpios = <&gpio TEGRA194_MAIN_GPIO(GG, 1) GPIO_ACTIVE_LOW>;
+
+		nvidia,refclk-select-gpios = <&gpio_aon TEGRA194_AON_GPIO(AA, 5)
+					      GPIO_ACTIVE_HIGH>;
+
+		phys = <&p2u_nvhs_0>, <&p2u_nvhs_1>, <&p2u_nvhs_2>,
+		       <&p2u_nvhs_3>, <&p2u_nvhs_4>, <&p2u_nvhs_5>,
+		       <&p2u_nvhs_6>, <&p2u_nvhs_7>;
+
+		phy-names = "p2u-0", "p2u-1", "p2u-2", "p2u-3", "p2u-4",
+			    "p2u-5", "p2u-6", "p2u-7";
+	};
+
 	fan: fan {
 		compatible = "pwm-fan";
 		pwms = <&pwm4 0 45334>;