ACPI: Disable Windows 8 compatibility for Lenovo ThinkPad T430s and X230

The AML implementation for brightness control on these machines contains
a workaround to meet the Windows 8 requirement of 101 brightness levels.
This implementation is flawed, as only 16 of the brighness values
reported by _BCL affect a change in brightness. _BCM silently discards
the rest of the values. Disabling Windows 8 compatibility on these
machines reverts them to the old behavior, making _BCL only report the
16 brightness levels which actually work. Add a quirk to do this along
with a dmi callback to disable Win8 compatibility.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=51231
BugLink: http://bugs.launchpad.net/bugs/1098216
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>