HID: multitouch: Synchronize MT frame on reset_resume

input_mt_get_slot_by_key() requires input_mt_sync_frame() to be called
at each frame. Do it when releasing the touches, or else we won't get
a proper slot number after mt_reset_resume().

Signed-off-by: Gabriele Mazzotta <gabriele.mzt@gmail.com>
Reviewed-by: Benson Leung <bleung@chromium.org>
Reviewed-by: Benjamin TIssoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>