Fix backlight control for Acer TravelMate B113 Laptop by adding
it to the video_dmi_table.

A workaround before that was to use acpi_osi=Linux or
acpi_backlight=vendor on boot but even then, only the function-
keys worked.

With this change there is no need for boot parameters and DE's
controls work as well.
Signed-off-by: Martin Kepplinger <martink@posteo.de>
[rjw: Subject]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>