As all level 2 and level 3 caches are unified, add required
cache-unified and cache-level properties to fix warnings like:
apm-mustang.dtb: l2-cache-0: 'cache-level' is a required property
apm-mustang.dtb: l2-cache-0: 'cache-unified' is a required property
Link: https://lore.kernel.org/r/20230421223139.115044-1-krzysztof.kozlowski@linaro.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>