ACPI: blacklist win8 OSI for ASUS Zenbook Prime UX31A

Since v3.7 the ACPI backlight driver doesn't work at all on this
machine, because presumably the backlight AML code in the ACPI
tables contains a code path that triggers when the OS identifies
itself as compatible with Windows 8 (which the kernel started to
do in 3.7).  That code path is never used by Windows and on this
particular machine it turns out to be unusable at all.

Work around this problem by blacklisting the win8 OSI, so we are back
to v3.6 behavior (that is, we don't tell the BIOS that we are
compatible with Windows 8).

Since v3.7, users have been forced to work around the initial
regression by modifying the boot arguments [1].

[1] https://wiki.archlinux.org/index.php/ASUS_Zenbook_Prime_UX31A



[rjw: Changelog]
Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>