PM / Runtime: Fix error path for prepare

If a device prepare callback for some reason would fail, the PM core
prevented the device from going inactive forever.

In this case, to reverse the pm_runtime_get_noresume() we invokes the
asyncronous pm_runtime_put(), thus restoring the usage count.
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/base/power/main.c

@@ -1277,6 +1277,9 @@ static int device_prepare(struct device *dev, pm_message_t state)
 
 	device_unlock(dev);
 
+	if (error)
+		pm_runtime_put(dev);
+
 	return error;
 }