ARM: dt: tegra: add bindings of power management configurations for PMC

The PMC mostly controls the entry and exit of the system from different
sleep modes. Different platform or system may have different configurations.
The power management configurations of PMC is represented as some properties.
The system needs to define the properties when the system supports deep sleep
mode (i.e. suspend).

Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: devicetree-discuss@lists.ozlabs.org
Signed-off-by: Joseph Lo <josephl@nvidia.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>