greybus: operation: fix operation ordering

Make the operation work queue single threaded.

The operation work queue was meant to be single threaded, but due to a
missing flag instead allowed one active task per CPU, something which
could lead to requests being processed out of order on SMP systems.
Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Tested-by: Rui Miguel Silva <rui.silva@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/operation.c

@@ -1043,7 +1043,8 @@ int __init gb_operation_init(void)
 	if (!gb_operation_cache)
 		goto err_destroy_message_cache;
 
-	gb_operation_workqueue = alloc_workqueue("greybus_operation", 0, 1);
+	gb_operation_workqueue = alloc_workqueue("greybus_operation",
+				WQ_UNBOUND, 1);
 	if (!gb_operation_workqueue)
 		goto err_operation;