arm64: dts: r8a7795: use fallback etheravb compatibility string

Use recently added fallback compatibility string in r8a7795 device tree.
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>

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

@@ -473,7 +473,8 @@ GIC_SPI 431 IRQ_TYPE_LEVEL_HIGH
 		};
 
 		avb: ethernet@e6800000 {
-			compatible = "renesas,etheravb-r8a7795";
+			compatible = "renesas,etheravb-r8a7795",
+				     "renesas,etheravb-rcar-gen3";
 			reg = <0 0xe6800000 0 0x800>, <0 0xe6a00000 0 0x10000>;
 			interrupts = <GIC_SPI 39 IRQ_TYPE_LEVEL_HIGH>,
 				     <GIC_SPI 40 IRQ_TYPE_LEVEL_HIGH>,