drm/i915: Don't use {skl, cnl}_hpd_pin() for bxt/glk

Just let bxt/glk fall back to intel_hpd_pin_default() instead
of using skl_hpd_pin() or cnl_hpd_pin(). Doesn't really matter
since both functions will end up returning the correct hpd pin
anyway, but I find it a bit less confusing when bxt/glk are
fully separated from the logic for the other platforms.

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210412054607.18133-5-ville.syrjala@linux.intel.com