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.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/soundwire/master.c

@@ -154,6 +154,7 @@ int sdw_master_device_add(struct sdw_bus *bus, struct device *parent,
 	bus->dev = &md->dev;
 	bus->md = md;
 
+	pm_runtime_enable(&bus->md->dev);
 device_register_err:
 	return ret;
 }
@@ -166,6 +167,7 @@ int sdw_master_device_add(struct sdw_bus *bus, struct device *parent,
  */
 int sdw_master_device_del(struct sdw_bus *bus)
 {
+	pm_runtime_disable(&bus->md->dev);
 	device_unregister(bus->dev);
 
 	return 0;