[Intel-gfx] Supporting fused display configurations v4

[Damien Lespiau]

Follow up of the v3:
  http://lists.freedesktop.org/archives/intel-gfx/2013-December/037333.html

The main change is the removal of INTEL_INFO() from the driver (patches 1 to
5), a clean-up suggested by Chris: the usage of that macro hides that we go
from dev to dev_priv while we could use the dev_priv pointer that is usually
available.

Patch 6 is also new, a minor clean-up while at it.

The remaining patches are rebased on top of the INTEL_INFO() change.

-- 
Damien