Staging: sst: Add runtime PM support

This adds runtime PM support for audio driver.
This also fixes LPA audio mode for moorestown platform

Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>