usb: typec: ucsi: displayport: Fix NULL pointer access

This patch ensures that the UCSI driver waits for all pending tasks in the
ucsi_displayport_work workqueue to finish executing before proceeding with
the partner removal.

Cc: stable <stable@kernel.org>
Fixes: af8622f6 ("usb: typec: ucsi: Support for DisplayPort alt mode")
Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Benson Leung <bleung@chromium.org>
Link: https://lore.kernel.org/r/20250424084429.3220757-3-akuchynski@chromium.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>