OMAP: PM counter infrastructure.

This patch provides the infrastructure to count how many times a
powerdomain entered a given power state (on, inactive, retention,
off). A number of functions are provided which will be called by the
chip specific powerdomain and clockdomain code whenever a transition
might have happened.

Signed-off-by: Peter 'p2' De Schrijver <peter.de-schrijver@nokia.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>