Some new Dell AIO systems have a button that generates a WMI event to
turn the LCD on/off.

BugLink: http://bugs.launchpad.net/bugs/1702541Signed-off-by: Alex Hung <alex.hung@canonical.com>
Acked-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>
(backported from commit ab9bb11c)
Signed-off-by: Alex Hung <alex.hung@canonical.com>
Acked-by: Colin Ian King <colin.king@canonical.com>
Acked-by: AceLan Kao <acelan.kao@canonical.com>
Acked-by: Po-Hsu Lin <po-hsu.lin@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>