ACPI: thinkpad-acpi: fix lenovo keymap for brightness

Starting in 2.6.23...

Several reports from X60 users complained that the default Lenovo keymap
issuing EV_KEY KEY_BRIGHTNESS_UP/DOWN input events caused major issues when
the proper brightness support through ACPI video.c was loaded.

Therefore, remove the generation of these events by default, which is the
right thing for T60, X60, R60, T61, X61 and R61 with their latest BIOSes.

Distros that want to misuse these events into OSD reporting (which requires
an ugly hack from hell in HAL) are welcome to set up the key map they need
through HAL.  That way, we don't break everyone else's systems.

Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Len Brown <len.brown@intel.com>