drm/i915/guc: Use correct context lock when callig clr_context_registered

s/ce/cn/ when grabbing guc_state.lock before calling
clr_context_registered.

Fixes: 0f7976506d ("drm/i915/guc: Rework and simplify locking")
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211214170500.28569-2-matthew.brost@intel.com
(cherry picked from commit b25db8c782)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c

@@ -1664,9 +1664,9 @@ static int steal_guc_id(struct intel_guc *guc, struct intel_context *ce)
 		list_del_init(&cn->guc_id.link);
 		ce->guc_id = cn->guc_id;
 
-		spin_lock(&ce->guc_state.lock);
+		spin_lock(&cn->guc_state.lock);
 		clr_context_registered(cn);
-		spin_unlock(&ce->guc_state.lock);
+		spin_unlock(&cn->guc_state.lock);
 
 		set_context_guc_id_invalid(cn);