drm/i915: Parametrize BXT_DE_PORT_HP_DDI with hpd_pin

Use hpd_pin to parametrize BXT_DE_PORT_HP_DDI() to make it clear
these have nothing to do with DDI ports or PHYs as such. The only
thing that matters is the HPD pin assignment.

v2: Remember the gvt

Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201028213323.5423-8-ville.syrjala@linux.intel.com