topstar-latop: ignore 0x82 event

Event 0x82 is emitted whenever a backlight event happens (brightness
change, backlight on/off).  For instance, when display is switched
off after a timeout, event 0x82 is emitted, and along with it a keypress
which switches the display back on again.

This patch adds 0x82 to the event ignore list so that the display stays
off when it is automatically switched off.

Signed-off-by: Manuel Lauss <manuel.lauss@googlemail.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>