drm/i915: Avoid taking the PPS lock for non-eDP/VLV/CHV

On ICL we have to make sure that we enable the AUX power domain in a
controlled way (corresponding to the port's actual TypeC mode). Since
the PPS lock - which takes an AUX power ref - is only needed on
eDP on all platforms and eDP/DP on VLV/CHV avoid taking it in all
other cases.

v2:
- Clarify commit log about the condition for taking the PPS lock.
  (Ville)

Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190509173446.31095-11-imre.deak@intel.com