ARM: shmobile: r8a7791: Add default PCIe bus clock

This patch adds a default PCIe bus clock node.
Signed-off-by: Phil Edworthy <phil.edworthy@renesas.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
[horms+renesas@verge.net.au: resolved conflict]
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm/boot/dts/r8a7791.dtsi

@@ -555,6 +555,15 @@ audio_clk_c: audio_clk_c {
 			clock-output-names = "audio_clk_c";
 		};
 
+		/* External PCIe clock - can be overridden by the board */
+		pcie_bus_clk: pcie_bus_clk {
+			compatible = "fixed-clock";
+			#clock-cells = <0>;
+			clock-frequency = <100000000>;
+			clock-output-names = "pcie_bus";
+			status = "disabled";
+		};
+
 		/* Special CPG clocks */
 		cpg_clocks: cpg_clocks@e6150000 {
 			compatible = "renesas,r8a7791-cpg-clocks",