psm(4): Add support for HP EliteBook 1040 ForcePads.

ForcePads do not have any physical buttons, instead they detect click
based on finger pressure. Forcepads erroneously report button click
if there are 2 or more fingers on the touchpad breaking multifinger
gestures. To workaround this start reporting a click only after
4 consecutive single touch packets has been received. Skip these packets
in case more contacts appear.

PR: 223369
Reported by: Neel Chauhan <neel@neelc.org>
Tested by: Neel Chauhan <neel@neelc.org>
Reviewed by: gonzo
Approved by: gonzo