arm64: dts: renesas: r8a779g3: Reinstate basic PCIe clock description for Sparrow Hawk

The 9FGV0441 PCIe clock generator can operate in autonomous mode, which
is the default mode. U-Boot currently does not have a driver for this
PCIe clock generator, but Linux 6.17 DT does describe the clock generator
in Sparrow Hawk board DT and this DT is included in U-Boot since commit
eea470fd7f ("Subtree merge tag 'v6.17-dts' of dts repo [1] into dts/upstream").

Reinstate basic PCIe clock description which matches the behavior of
Linux DT before Linux 6.17.y release in in U-Boot DT extras to allow
PCIe to be used on Sparrow Hawk board in U-Boot until the 9FGV0441
driver gets implemented or ported from Linux.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>

arch/arm/dts/r8a779g3-sparrow-hawk-u-boot.dtsi

@@ -49,6 +49,24 @@
 	status = "okay";
 };
 
+&pcie0_clkref {
+	clock-frequency = <100000000>;
+	status = "okay";
+};
+
+&pciec0 {
+	clocks = <&cpg CPG_MOD 624>, <&pcie0_clkref>;
+};
+
+&pcie1_clkref {
+	clock-frequency = <100000000>;
+	status = "okay";
+};
+
+&pciec1 {
+	clocks = <&cpg CPG_MOD 625>, <&pcie1_clkref>;
+};
+
 &rpc {
 	flash@0 {
 		/*