Input: sentelic - only report position of first finger as ST coordinates

Report only the position of the first finger as absolute non-MT coordinates,
instead of reporting both fingers alternatively. Actual MT events are
unaffected.

This fixes horizontal and improves vertical scrolling with the touchpad.

Cc: stable@vger.kernel.org
Signed-off-by: Christophe TORDEUX <christophe@tordeux.net>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>