This patch adds detection of trackstick for v7 protocol devices. Code in
this patch is used in official Dell touchpad linux drivers for Dell models:
Dell Latitude E5250/5250, E5450/5450, E5550/5550

Detection code and base reg for alps v3 rushmore and v7 devices is exacly
same.

Also user in bug https://bugzilla.kernel.org/show_bug.cgi?id=94801 reported
that Toshiba Sattellite Z30-A-1DG has only alps v7 touchpad device without
trackstick and kernel reports to userspace also redundant trackstick
device.
Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Tested-by: Alex Hung <alex.hung@canonical.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>