OMAP: PM: Add pm-debug counters

This patch provides the debugfs entries and a function which will be
called by the PM code to register the time spent per domain per
state. Also some new fields are added to the powerdomain struct to
keep the time information.

NOTE: As of v2.6.29, using getnstimeofday() after drivers are
suspended is no longer safe since the timekeeping subsystem is also
suspended as part of the suspend process.  Instead use sched_clock()
which on OMAP returns the 32k SYNC timer in nanoseconds.

Also, do not print out status for meta powerdomains (dpll*)

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