ARM: dts: r8a7790: use fallback pci compatibility string

Use recently added fallback compatibility string in r8a7790 device tree.
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm/boot/dts/r8a7790.dtsi

@@ -1499,7 +1499,7 @@ xhci: usb@ee000000 {
 	};
 
 	pci0: pci@ee090000 {
-		compatible = "renesas,pci-r8a7790";
+		compatible = "renesas,pci-r8a7790", "renesas,pci-rcar-gen2";
 		device_type = "pci";
 		reg = <0 0xee090000 0 0xc00>,
 		      <0 0xee080000 0 0x1100>;
@@ -1534,7 +1534,7 @@ usb@0,2 {
 	};
 
 	pci1: pci@ee0b0000 {
-		compatible = "renesas,pci-r8a7790";
+		compatible = "renesas,pci-r8a7790", "renesas,pci-rcar-gen2";
 		device_type = "pci";
 		reg = <0 0xee0b0000 0 0xc00>,
 		      <0 0xee0a0000 0 0x1100>;
@@ -1555,7 +1555,7 @@ pci1: pci@ee0b0000 {
 	};
 
 	pci2: pci@ee0d0000 {
-		compatible = "renesas,pci-r8a7790";
+		compatible = "renesas,pci-r8a7790", "renesas,pci-rcar-gen2";
 		device_type = "pci";
 		clocks = <&mstp7_clks R8A7790_CLK_EHCI>;
 		power-domains = <&cpg_clocks>;