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

  meson-a1-ad401.dtb: l2-cache0: 'cache-unified' is a required property
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Link: https://lore.kernel.org/r/20230421223211.115612-1-krzysztof.kozlowski@linaro.orgSigned-off-by: Neil Armstrong <neil.armstrong@linaro.org>