clk: tegra: Add suspend and resume support on Tegra210

All the CAR controller settings are lost on suspend when core power goes
off. This implement saving and restoring context for all PLLs and clocks
during system suspend and resume to have the clocks back to same state
for normal operation.

Clock driver suspend and resume are registered as syscore_ops as clocks
restore need to happen before the other drivers resume to have all their
clocks back to the same state as before suspend.

Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>