arm64: dts: renesas: r8a779f0: spider: Enable PCIe Host ch0

Enable PCIe Host controller channel 0 on R-Car S4-8 Spider board.

Since this board has an Oculink connector, CLKREQ# pin of PFC for PCIe
should not be used. So, using a GPIO is used to output the clock instead.
Otherwise the controller cannot detect a PCIe device.
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20230905012404.2915246-3-yoshihiro.shimoda.uh@renesas.comSigned-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

arch/arm64/boot/dts/renesas/r8a779f0-spider-cpu.dtsi

@@ -53,6 +53,12 @@ memory@480000000 {
 		reg = <0x4 0x80000000 0x0 0x80000000>;
 	};
 
+	rc21012_pci: clk-rc21012-pci {
+		compatible = "fixed-clock";
+		clock-frequency = <100000000>;
+		#clock-cells = <0>;
+	};
+
 	rc21012_ufs: clk-rc21012-ufs {
 		compatible = "fixed-clock";
 		clock-frequency = <38400000>;
@@ -106,6 +112,12 @@ gpio_exp_20: gpio@20 {
 		reg = <0x20>;
 		gpio-controller;
 		#gpio-cells = <2>;
+
+		rc21012-gpio2-hog {
+			gpio-hog;
+			gpios = <5 GPIO_ACTIVE_LOW>;
+			output-high;
+		};
 	};
 };
 
@@ -145,6 +157,18 @@ &mmc0 {
 	status = "okay";
 };
 
+&pcie0_clkref {
+	compatible = "gpio-gate-clock";
+	clocks = <&rc21012_pci>;
+	enable-gpios = <&gpio2 15 GPIO_ACTIVE_LOW>;
+	/delete-property/ clock-frequency;
+};
+
+&pciec0 {
+	reset-gpio = <&gpio_exp_20 0 GPIO_ACTIVE_LOW>;
+	status = "okay";
+};
+
 &pfc {
 	pinctrl-0 = <&scif_clk_pins>;
 	pinctrl-names = "default";