drm/bridge_connector: drop drm_bridge_connector_en/disable_hpd()

drm/bridge_connector: drop drm_bridge_connector_en/disable_hpd()

Now as all drivers stopped calling drm_bridge_connector_enable_hpd() and
drm_bridge_connector_disable_hpd() it is safe to remove them complelely.
Rename our internal helpers to remove the underscore prefix.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20221102180705.459294-8-dmitry.baryshkov@linaro.org