arm64: tegra: Add missing cache properties on Tegra210

As all level 2 and level 3 caches are unified, add required
cache-unified property to fix warnings like:

  tegra210-p2371-0000.dtb: l2-cache: 'cache-unified' is a required property
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>

arch/arm64/boot/dts/nvidia/tegra210.dtsi

@@ -2000,6 +2000,7 @@ CPU_SLEEP: cpu-sleep {
 		L2: l2-cache {
 			compatible = "cache";
 			cache-level = <2>;
+			cache-unified;
 		};
 	};