ACPI: Properly clear flags on false-positives and send uevent on sudden unplug

Some devices emit a ACPI_NOTIFY_DEVICE_CHECK while physically unplugging
even if the software undock has already been done and dock_present() check
fails. However, the internal flags need to be cleared (complete_undock()).

Also, even notify userspace if the dock station suddently went away
without proper software undocking.

This happens on a Acer TravelMate 3000

Signed-off-by: Holger Macht <hmacht@suse.de>
Signed-off-by: Andi Kleen <ak@linux.intel.com>