drm/i915: Define HSW/BDW display power domains the right way up

Currently we're trying to define HSW/BDW power wells by what's not
included. Let's do it the other way around, so that you can actually
tell when the power well would get enabled. This will also allow us to
add new power domains without accidentally adding it to the HSW/BDW
display power domains.

The current set of domains looks rather buggy even:
- POWER_DOMAIN_MODESET is included in the display power well needlessly
- DDI-B to DDI-E were not part of the display power well when they
  should be

So let's fix that up while at it.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1460977348-32260-4-git-send-email-ville.syrjala@linux.intel.com


Reviewed-by: Imre Deak <imre.deak@intel.com>