soundwire: master: enable pm runtime

soundwire: master: enable pm runtime

The hierarchy of soundwire devices is platform device -> M device -> S
device. A S device is physically attached on the platform device. So the
platform device should be resumed when a S device is resumed. As the
bridge of platform device and S device, we have to implement runtime pm
on M driver. We have set runtime pm ops in M driver already, but still
need to enable runtime pm.

Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Link: https://lore.kernel.org/r/20200726215945.3119-1-yung-chuan.liao@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>