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>