drm/i915: get port power domain in connector detect handlers

The connector detect and get_mode handlers need to access the port
specific HW blocks to read the EDID etc. Get/put the port power domains
around these handlers.

v2:
- get port power domain for HDMI too (Ville)
- get port power domain for the DP,HDMI audio detect handlers (Jesse)
- Leave the intel_runtime_pm_get/put in the DP detect function in place.
  Instead of just removing them, these should be moved to the appropriate
  power_well enable/disable handlers. We can do this after Paulo's
  'Merge PC8 with runtime PM, v2' patchset.
v3:
- rebased on latest -nightly

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>