arm/tegra: implement support for tegra30

Add support for tegra30 SoC. This includes a device tree compatible type for
this SoC ("nvidia,tegra30") and adds L2 cache initialization for this new SoC.
The clock framework is still missing, which prevents most drivers from working.
The basic IRQs are the same, so remove the dependency on
CONFIG_ARCH_TEGRA_2x_SOC.

Signed-off-by: Peter De Schrijver <pdeschrijver@nvidia.com>
Acked-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Colin Cross <ccross@android.com>
Signed-off-by: Olof Johansson <olof@lixom.net>