Input: wistron - add mapping for Wistron MS 2111

Wistron MS 2111 (aka Medion 'Titanium' MD 9783, aka ALDI PC,
aka Fujitsu-Siemens AMILO D7800, aka ...) has 5 extra buttons,
map them. Unfortunately we only have DMI data for the Medion
box.

Signed-off-by: Dmitry Torokhov <dtor@mail.ru>