Input: wistron_btns - drop bogus MODULE_VERSION macro

MODULE_VERSION is pointless for an in-kernel module and git log confirms that
it has never been actually maintained as well (bumped a single time, despite
quite major feature additions later on, which haven't been reflected in
MODULE_VERSION).

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