ARM: tegra: support for Tegra30 CPU powerdomains

Secondary CPU powerdomains can be powergated on Tegra30. Add the necessary
functions to do this. This will be used to boot the secondary CPUs later on.

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