Use pointer mode instead of spots for SEMI_MT touch pads.

The spot-based presentation relies on being able to accurately
locate and distinguish two or more fingers on the touch pad.
We can still do gesture recognition without distinct multitouch
but it doesn't make sense to show spots because we can't be sure
that the spots will appear in the right places.

Change-Id: Ia282d77000bf3b50d395273a1f0ac0bbe55b3c6f