Add Runtime PM support to the CMT driver.

The hardware device is enabled as long as the clocksource
or the clockevent portion of the driver is used.
Signed-off-by: NMagnus Damm <damm@opensource.se>
Acked-by: NJohn Stultz <johnstul@us.ibm.com>
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>