wsp: Allow the trackpad to be used after a partially unreleased click.

This provides functionality for a click which is partially unreleased
and then allows the user to continue moving the mousepad as if were not
invoked as a full click

Signed-off-by: Joshua Rogers <Joshua@Joshua.Hu>
Reviewed by: imp, wulf
Pull Request: https://github.com/freebsd/freebsd-src/pull/1365