drm/i915: Disable hotplug detection works during driver init/shutdown

As described in the previous patch, an unexpected connector
detection/modeset started from the intel_hotplug::hotplug_work can
happen during the driver init/shutdown sequence. Prevent these by
disabling the queuing of and flushing all the intel_hotplug work that
can start them at the beginning of the init/shutdown sequence and allow
the queuing only while the display is in the initialized state.

Other work items - like the intel_connector::modeset_retry_work or the
MST probe works - are still enabled and can start a detection/modeset,
but after the previous patch these will be rejected. Disabling these
works as well is for a follow-up patchset.

Link: https://patchwork.freedesktop.org/patch/msgid/20240104083008.2715733-9-imre.deak@intel.com


Reviewed-by: Jouni Högander <jouni.hogander@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>