arm64: dts: r8a7795: Use Gen 3 fallback compat string for PCIE

Use recently added en 3 fallback compat string for PCIE
in r8a7795 DT.
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>

arch/arm64/boot/dts/renesas/r8a7795.dtsi

@@ -1279,7 +1279,8 @@ hsusb: usb@e6590000 {
 		};
 
 		pciec0: pcie@fe000000 {
-			compatible = "renesas,pcie-r8a7795";
+			compatible = "renesas,pcie-r8a7795",
+				     "renesas,pcie-rcar-gen3";
 			reg = <0 0xfe000000 0 0x80000>;
 			#address-cells = <3>;
 			#size-cells = <2>;
@@ -1304,7 +1305,8 @@ pciec0: pcie@fe000000 {
 		};
 
 		pciec1: pcie@ee800000 {
-			compatible = "renesas,pcie-r8a7795";
+			compatible = "renesas,pcie-r8a7795",
+				     "renesas,pcie-rcar-gen3";
 			reg = <0 0xee800000 0 0x80000>;
 			#address-cells = <3>;
 			#size-cells = <2>;