drm/i915: Split icp_hpd_detection_setup() into ddi vs. tc parts

No reason to stuff both DDI and TC port handling into the same
function. Split it into two.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200630215601.28557-9-ville.syrjala@linux.intel.com
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>