ACPI: thinkpad-acpi: revert keymap changes

Revert commit fba956c4

, "Map volume and
brightness events on thinkpads".

That commit made some modifications to the default keymaps that cause bad
behaviour on all IBM ThinkPads if HAL doesn't know to change them into
passive (on-screen-display only) events.

The proper solution for IBM ThinkPads is to use the _NOTIFY version of the
key codes for the IBM default map (which are not available in mainline
yet), and for the Lenovo keymap, it will take some studying of the various
DSDTs and testing to know the best path (which I will do shortly).

For more data, refer to:
http://thread.gmane.org/gmane.linux.kernel/591037/focus=591045

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