PM / sleep: unregister wakeup source when disabling device wakeup

When enabling a device' wakeup capability, a wakeup source
is created for the device automatically. But the wakeup source
is not unregistered when disabling the device' wakeup capability.

This results in zombie wakeup sources, after devices/drivers are unregistered.

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c
index 2d56f41..eb1bd2e 100644
--- a/drivers/base/power/wakeup.c
+++ b/drivers/base/power/wakeup.c
@@ -318,10 +318,16 @@
 {
 	int ret = 0;
 
+	if (!dev)
+		return -EINVAL;
+
 	if (enable) {
 		device_set_wakeup_capable(dev, true);
 		ret = device_wakeup_enable(dev);
 	} else {
+		if (dev->power.can_wakeup)
+			device_wakeup_disable(dev);
+
 		device_set_wakeup_capable(dev, false);
 	}