HID: multitouch: add support for Win 8.1 multitouch touchpads

Multitouch touchpads built for Win 8.1 need to be sent an input mode feature report
in order to start reporting multitouch events. This is the same process sent
to Win 7 multitouch touchscreens except the value of the feature report is 3 for
touchpads.

Signed-off-by: Andrew Duggan <aduggan@synaptics.com>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>