drm/i915: Move hpd_pin setup to encoder init

Currently DP/HDMI/DDI encoders init their hpd_pin from the
connector init. Let's move it to the encoder init so that
we don't need to add platform specific junk to the connector
init (which is shared by all g4x+ platforms).

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200630215601.28557-10-ville.syrjala@linux.intel.com
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>