Input: ALPS - update documentation for recent touchpad driver mods

Updated documentation for the new ALPS touchpad support submitted in two
patchsets by Kevin Cernekee.  My understanding is the most recent
patchset '"Dolphin V2" touchpad support' may still need some work but
Future work on the ALPS driver should not impact these documentation changes.

See https://bugs.launchpad.net/ubuntu/+source/linux/+bug/606238

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