ACPI: video: Add backlight=native DMI quirk for Lenovo Ideapad Z470

The Lenovo Ideapad Z470 predates Windows 8, so it defaults to using
acpi_video for backlight control. But this is not functional on this
model.

Add a DMI quirk to use the native backlight interface which works.

Link: https://bugzilla.suse.com/show_bug.cgi?id=1208724
Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>