PM / runtime: Drop usage count for suppliers at device link removal

In the case consumer device is runtime resumed, while the link to the
supplier is removed, the earlier call to pm_runtime_get_sync() made from
rpm_get_suppliers() does not get properly balanced with a corresponding
call to pm_runtime_put(). This leads to that suppliers remains to be
runtime resumed forever, while they don't need to.

Let's fix the behaviour by calling rpm_put_suppliers() when dropping a
device link. Not that, since rpm_put_suppliers() checks the
link->rpm_active flag, we can correctly avoid to call pm_runtime_put() in
cases when we shouldn't.

Reported-by: Todor Tomov <todor.tomov@linaro.org>
Fixes: 21d5c57b3726 (PM / runtime: Use device links)
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/base/power/runtime.c

@@ -1586,6 +1586,8 @@ void pm_runtime_new_link(struct device *dev)
 
 void pm_runtime_drop_link(struct device *dev)
 {
+	rpm_put_suppliers(dev);
+
 	spin_lock_irq(&dev->power.lock);
 	WARN_ON(dev->power.links_count == 0);
 	dev->power.links_count--;