Acer Extensa 5235, TravelMate 5760 and Aspire 5750 laptop have broken _BCM
implemenation, the AML code wrote value to EC register but firmware didn't
change brighenss.

Fortunately, the brightness control works on those machines with vendor mode.
So, add this machine to video backlight vendor mode quirk table.

Reference: bko#36322
        https://bugzilla.kernel.org/show_bug.cgi?id=36322
Reference: bko#42833
        https://bugzilla.kernel.org/show_bug.cgi?id=42833
Reference: bko#42993
        https://bugzilla.kernel.org/show_bug.cgi?id=42993

Cc: Christopher M. Penalver <christopher.penalver@gmx.com>
Cc: Bence Lukacs <lukacs.bence1@gmail.com>
Cc: Joern Heissler <kernelbugs2012@joern.heissler.de>
Cc: Carlos Corbacho <carlos@strangeworlds.co.uk>
Cc: Matthew Garrett <mjg@redhat.com>
Cc: Dmitry Torokhov <dtor@mail.ru>
Cc: Corentin Chary <corentincj@iksaif.net>
Cc: Thomas Renninger <trenn@suse.de>
Signed-off-by: Lee, Chun-Yi <jlee@suse.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>