ARM: dts: r8a7792: Use R-Car SDHI Gen2 fallback compat string

Use newly added R-Car SDHI Gen2 fallback compat string
in the DT of the r8a7792 SoC.

This should have no run-time effect as the driver matches against
the per-SoC compat string before considering the fallback compat string.
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm/boot/dts/r8a7792.dtsi

@@ -507,7 +507,8 @@ smp-sram@0 {
 		};
 
 		sdhi0: sd@ee100000 {
-			compatible = "renesas,sdhi-r8a7792";
+			compatible = "renesas,sdhi-r8a7792",
+				     "renesas,rcar-gen2-sdhi";
 			reg = <0 0xee100000 0 0x328>;
 			interrupts = <0 165 IRQ_TYPE_LEVEL_HIGH>;
 			dmas = <&dmac0 0xcd>, <&dmac0 0xce>,