drm reference counter connectors and fix lifetimes

[Dave Airlie]

I've been trolled since I did MST that I really didn't do a good job
on the connector lifetimes, so I finally felt guilty and had time to try
and fix this up.

This is a set of patches to handle connector lifetimes so that the connectors
don't go away in the middle of us doing something. I've done some testing
on this with kms_flip on my haswell laptop while undocking etc.

Daniel has been pestering me to finish it off, so I've cleaned up the last
few things in the mst patches at least for i915 and decided to send it out.

Dave.