ARM: dts: r8a7794: use fallback usbhs compatibility string

Use recently added fallback compatibility string in r8a7794 device tree.
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>

arch/arm/boot/dts/r8a7794.dtsi

@@ -724,7 +724,7 @@ usb@0,2 {
 	};
 
 	hsusb: usb@e6590000 {
-		compatible = "renesas,usbhs-r8a7794";
+		compatible = "renesas,usbhs-r8a7794", "renesas,rcar-gen2-usbhs";
 		reg = <0 0xe6590000 0 0x100>;
 		interrupts = <0 107 IRQ_TYPE_LEVEL_HIGH>;
 		clocks = <&mstp7_clks R8A7794_CLK_HSUSB>;