drm/i915: Don't change the status of forced connectors during HPD poll detect

As described in the previous patch a connector shouldn't change its
status while it's forced to a connected/disconnected state. This can
still happen while running the connector detect function to account for
lost HPD events in a low-power state.

Fix this by reusing the connector detect function which handles a
hotplug event and prevents updating the status for forced connectors as
expected.

Testcase: igt@kms_force_connector_basic@force-connector-state
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Jouni Högander <jouni.hogander@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230809104307.1218058-3-imre.deak@intel.com