pwr: Add power states to ClockedObject

pwr: Add power states to ClockedObject

Add 4 power states to the ClockedObject, provides necessary access
functions to check and update the power state. Default power state
is UNDEFINED, it is responsibility of the respective simulation
model to provide the startup state and any other logic for state
change. Add number of transition stat. Add distribution of time
spent in clock gated state. Add power state residency stat. Add
dump call back function to allow stats update of distribution
and residency stats.

Change-Id: Id086090a2ed720c9fcb37812a3c98f0f724907c6