drm: drm_probe_helper: Fix output_poll_work scheduling

drm: drm_probe_helper: Fix output_poll_work scheduling

drm_kms_helper_poll_enable_locked() should check if we have delayed event
pending and if we have, schedule the work to run without delay.

Currently the output_poll_work is only scheduled if any of the connectors
have DRM_CONNECTOR_POLL_CONNECT or DRM_CONNECTOR_POLL_DISCONNECT with
DRM_OUTPUT_POLL_PERIOD delay. It does not matter if we have delayed event
already registered to be handled. The detection will be delayd by
DRM_OUTPUT_POLL_PERIOD in any case.
Furthermore if none of the connectors are marked as POLL_CONNECT or
POLL_DISCONNECT because all connectors are either POLL_HPD or they are
always connected: the output_poll_work will not run at all even if we
have delayed event marked.

When none of the connectors require polling, their initial status change
from unknown to connected/disconnected is not going to be handled until
the first kms application starts or if we have fb console enabled.

Note that in general the output poll work should be enabled already
when this happens, but at driver load usually the first probe happens
before the output polling is enabled. This patch fixes this case.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
[danvet: Note when exactly this is an issue, since the probe code
schedules the poll work itself already.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20160831110905.31289-1-peter.ujfalusi@ti.com