drm: Fix output poll work for drm_kms_helper_poll=n

If drm_kms_helper_poll=n the output poll work will only get scheduled
from drm_helper_probe_single_connector_modes() to handle a delayed
hotplug event. Since polling is disabled the work in this case should
just call drm_kms_helper_hotplug_event() w/o detecting the state of
connectors and rescheduling the work.

After commit d33a54e3 after a delayed hotplug event above the
connectors did get re-detected in the poll work and the work got
re-scheduled periodically (since poll_running is also false if
drm_kms_helper_poll=n), in effect ignoring the drm_kms_helper_poll=n
kernel param.

Fix the above by calling only drm_kms_helper_hotplug_event() for a
delayed hotplug event if drm_kms_helper_hotplug_event=n, as was done
before d33a54e3.

Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Fixes: d33a54e3 ("drm/probe_helper: sort out poll_running vs poll_enabled")
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240301152243.1670573-1-imre.deak@intel.com