Input: ALPS - fix TrackStick Y axis handling for SS5 hardware

A minus character was lost in commit 23fce365, causing the Y axis to be
inverted for SS5 TrackStick events.  (Pushing the TrackStick up caused
the pointer to move down, and vice versa.)  Restore the lost minus.

Fixes: 23fce365

 ("Input: ALPS - clean up code for SS5 hardware")
Signed-off-by: Paul Donohue <linux-kernel@PaulSD.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>