ACPI: Set flag DOCK_UNDOCKING when triggered via sysfs

begin_undock() is only called when triggered via a acpi notify handler
(pressing the undock button on the dock station), but complete_undock() is
always called after the eject. So if a undock is triggered through a sysfs
write, the flag DOCK_UNDOCKING has to be set for the dock station,
too. Otherwise this will freeze the system hard.
Signed-off-by: NHolger Macht <hmacht@suse.de>
Acked-by: NKristen Carlson Accardi <kristen.c.accardi@intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLen Brown <len.brown@intel.com>

drivers/acpi/dock.c

@@ -710,6 +710,7 @@ static ssize_t write_undock(struct device *dev, struct device_attribute *attr,
 	if (!count)
 		return -EINVAL;
 
+	begin_undock(dock_station);
 	ret = handle_eject_request(dock_station, ACPI_NOTIFY_EJECT_REQUEST);
 	return ret ? ret: count;
 }