ARM: dts: r8a7793: Add L2 cache-controller node

Add a device node for the L2 cache, and link the CPU node to it.

The L2 cache for the Cortex-A15 CPU cores is 1 MiB large (organized as
64 KiB x 16 ways).

Signed-off-by: Geert Uytterhoeven <[e-mail]>
Signed-off-by: Simon Horman <[e-mail]>

arch/arm/boot/dts/r8a7793.dtsi

···
 					   < 937500 1000000>,
 					   < 750000 1000000>,
 					   < 375000 1000000>;
+			next-level-cache = <&L2_CA15>;
 		};
 	};
 
···
 			cooling-maps {
 			};
 		};
+	};
+
+	L2_CA15: cache-controller@0 {
+		compatible = "cache";
+		cache-unified;
+		cache-level = <2>;
 	};
 
 	gic: interrupt-controller@f1001000 {