ARM: tegra: introduce tegra_cpu_car_ops structures

The tegra_cpu_car_ops provide the interface for CPU to control
it's clock gating and reset status. The other drivers should use
this for CPU control. And should not directly access CAR registers
to control CPU.

Signed-off-by: Joseph Lo <josephl@nvidia.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>