arm64: dts: allwinner: a64: Add L2 cache nodes

Current kernels complain when booting on an A64 Soc:
....
[    1.904297] cacheinfo: Unable to detect cache hierarchy for CPU 0
....
Not a real biggie on this flat topology, but also easy enough to fix.

Add the L2 cache node and let each CPU point to it.
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Chen-Yu Tsai <wens@csie.org>

arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi

@@ -88,6 +88,7 @@ cpu0: cpu@0 {
 			device_type = "cpu";
 			reg = <0>;
 			enable-method = "psci";
+			next-level-cache = <&L2>;
 		};
 
 		cpu1: cpu@1 {
@@ -95,6 +96,7 @@ cpu1: cpu@1 {
 			device_type = "cpu";
 			reg = <1>;
 			enable-method = "psci";
+			next-level-cache = <&L2>;
 		};
 
 		cpu2: cpu@2 {
@@ -102,6 +104,7 @@ cpu2: cpu@2 {
 			device_type = "cpu";
 			reg = <2>;
 			enable-method = "psci";
+			next-level-cache = <&L2>;
 		};
 
 		cpu3: cpu@3 {
@@ -109,6 +112,12 @@ cpu3: cpu@3 {
 			device_type = "cpu";
 			reg = <3>;
 			enable-method = "psci";
+			next-level-cache = <&L2>;
+		};
+
+		L2: l2-cache {
+			compatible = "cache";
+			cache-level = <2>;
 		};
 	};