thinkpad-acpi: fix incorrect use of TPACPI_BRGHT_MODE_ECNVRAM

HBRV-based default selection of backlight control strategy didn't work
well, at least the X41 defines it but doesn't use it and I don't think
it will stop there.

Switch to a white/blacklist.  All models that have HBRV defined have
been included in the list, and initially all ATI GPUs will get
ECNVRAM, and the Intel GPUs will get UCMS_STEP.

Symptoms of incorrect backlight mode selection are:

1. Non-working backlight control through sysfs;

2. Backlight gets reset to the lowest level at every shutdown, reboot
   and when thinkpad-acpi gets unloaded;

This fixes a regression in 2.6.30, bugzilla #13826

Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Reported-by: Tobias Diedrich <ranma+kernel@tdiedrich.de>
Cc: stable@kernel.org
Signed-off-by: Len Brown <len.brown@intel.com>