drm/xe/guc: Synchronize Dead CT worker with unbind

drm/xe/guc: Synchronize Dead CT worker with unbind

Cancel and wait for any Dead CT worker to complete before continuing
with device unbinding. Else the worker will end up using resources freed
by the undind operation.

Cc: Zhanjun Dong <zhanjun.dong@intel.com>
Fixes: d2c5a5a926f4 ("drm/xe/guc: Dead CT helper")
Signed-off-by: Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com>
Reviewed-by: Stuart Summers <stuart.summers@intel.com>
Link: https://patch.msgid.link/20251103123144.3231829-6-balasubramani.vivekanandan@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>