drm/i915: Init aux_ch for HDMI ports too

From ICL onwards DDI/TypeC ports - even in HDMI static mode - need to know
which AUX CH belongs to them, so initialize aux_ch for those ports too.
For consistency do this for all HDMI ports, not only for DDI/TypeC ones.

Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: José Roberto de Souza <jose.souza@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181101140427.31026-4-imre.deak@intel.com