Input: add Wistron driver

Input: add Wistron driver

A driver for laptop buttons using an x86 BIOS interface that is
apparently used on quite a few laptops and seems to be originating
from Wistron.

This driver currently "knows" only about Fujitsu-Siemens Amilo Pro V2000
(i.e. it can detect the laptop using DMI and it contains the
keycode->key meaning mapping for this laptop) and Xeron SonicPro X 155G
(probably can't be reliably autodetected, requires a module parameter),
adding other laptops should be easy.

In addition to reporting button presses to the input layer the driver
also allows enabling/disabling the embedded wireless NIC (using the
"Wifi" button); this is done using the same BIOS interface, so it seems
only logical to keep the implementation together.  Any flexibility
possibly gained by allowing users to remap the function of the "Wifi"
button is IMHO not worth it when weighted against the necessity to run
an user-space daemon to convert button presses to wifi state changes.

Signed-off-by: Miloslav Trmac <mitr@volny.cz>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>