Input: alps - add sanity checks for non DualPoint devices

Make sure that driver does not process bogus packets as trackstick data
when there is no trackstick present and emit warnings in dmesg so potential
issues with trackstick handling will be visible for debugging.

Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>