Input: wistron_btns - add MODULE_DEVICE_TABLE

This allows the wistron_btns module to be autoloaded on boot, its functionality
is required to support the hardware rfkill switches on most of the supported
notebooks, in order to unblock the hard blocked rfkill state for wireless and
bluetooth devices.

Tested on a Medion MD96500:
alias:          dmi*:svn*MEDIONPC*:pn*WIM2040*:

Signed-off-by: Stefan Lippers-Hollmann <s.l-h@gmx.de>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>