Non interleaved V2 dualpoint touchpad / stick combos have separate stick
button bits in the touchpad packets, if we do not check these then the
trackpoint buttons will not work when using the touchpad, and when pressed
when the user starts using the touchpad will report a release event even
though the button is still pressed.

This commit fixes this by checking the separate bits, note that we simply
combine the buttons, since the hardware does the same when using the touchpad
buttons with the trackpoint, so we do not have enough information to properly
separate them.
Reported-by: Hans de Bruin <jmdebruin@xmsnet.nl>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>