hp-wmi: notify of a potential docking state change on resume

It is possible that the system gets docked or undocked while it's
suspended. Generate an input event on resume to notify user space
if there was a state change.

As it is a switch, we can generate the event unconditionally; the
input layer will only pass it on if there is an actual change.

Signed-off-by: Frans Pop <elendil@planet.nl>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>