ARM: shmobile: r8a73a4: Add SoC-specific CMT compatible property

The CMT1 timer used the generic compatible property only.
Add the SoC-specific one, which is already documented, to make it future
proof.
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: NSimon Horman <horms+renesas@verge.net.au>

arch/arm/boot/dts/r8a73a4.dtsi

@@ -114,7 +114,7 @@
 	};
 
 	cmt1: timer@e6130000 {
-		compatible = "renesas,cmt-48-gen2";
+		compatible = "renesas,cmt-48-r8a73a4", "renesas,cmt-48-gen2";
 		reg = <0 0xe6130000 0 0x1004>;
 		interrupts = <0 120 IRQ_TYPE_LEVEL_HIGH>;