Add a WMI driver for Dell laptops. Currently it does nothing but send a
generic input event when a button with a picture of a battery on it is
pressed, but maybe other uses will appear over time.
Signed-off-by: Matthew Garrett <mjg@redhat.com> Cc: Dmitry Torokhov <dtor@mail.ru> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Len Brown <len.brown@intel.com>