thinkpad_acpi: Add support for more adaptive kbd buttons

This commit adds new elements to the ThinkPad keymaps, and
will send key events for keys for which an input.h declaration
exists.

Signed-off-by: Bastien Nocera <hadess@hadess.net>
Reviewed-by: Henrique de Moraes Holschuh <hmh@hyymh.eng.br>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>