Input: ALPS - enable trackstick on Rushmore touchpads

Separate out the common trackstick probe/setup sequences, then call them
from each of the v3 init functions.

Credits: Emmanual Thome furnished the information on the trackstick init
and how it affected the report format.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
Tested-by: Dave Turvene <dturvene@dahetral.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>