ARM: shmobile: Use r8a7791 suffix for IRQC compat string

Add "renesas,irqc-r8a7791" to the compatible string for IRQC
in case of r8a7791. This makes the IRQC follow the same style
as the other devices and also makes it more future proof.
Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm/boot/dts/r8a7791.dtsi

@@ -154,7 +154,7 @@ timer {
 	};
 
 	irqc0: interrupt-controller@e61c0000 {
-		compatible = "renesas,irqc";
+		compatible = "renesas,irqc-r8a7791", "renesas,irqc";
 		#interrupt-cells = <2>;
 		interrupt-controller;
 		reg = <0 0xe61c0000 0 0x200>;