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

  s32g274a-evb.dtb: l2-cache1: 'cache-unified' is a required property
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Matthias Brugger <mbrugger@suse.com>
Signed-off-by: Chester Lin <clin@suse.com>
Link: https://lore.kernel.org/r/20230421223202.115472-1-krzysztof.kozlowski@linaro.org