[RFC] DisplayPort MST v0.3

[Dave Airlie]

Hi,

A repost of the current state of the displayport MST support for
i915, mainly targetted the Lenovo docks.

Major changes since last posting:
add a path blob property for userspace to use to track topology
provide reference counting, locking and lookups for branch and port structs.
some DocBook!
fix i915 problems with DPMS - ordering of link bring up.
aux channel locking - this should be pushed down I think into the aux helpers,

TODO:
fbcon support:
fix non 4 lane 5.4Ghz.
fix more of state checker harder.

Dave.