drm/i915: Use encoder->devdata in eDP init

Since we now populate encoder->devdata for all DP capable
platforms we can consult it directly during the eDP
connector init instead of taking a detour via some global
list/array.

Unfortunately we can't quite get rid of
intel_dp_is_port_edp() since it's still used by the higher
level ilk/vlv/chv output setup code.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230208015508.24824-11-ville.syrjala@linux.intel.com


Reviewed-by: Jani Nikula <jani.nikula@intel.com>