!4794 serial: imx: fix tx statemachine deadlock

Merge Pull Request from: @ci-robot 
 
PR sync from: felix <fuzhen5@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/GSOELNXX7EAKIWBCNWFS7IXZSOLORM77/ 
 
https://gitee.com/src-openeuler/kernel/issues/I93EEE 
 
Link:https://gitee.com/openeuler/kernel/pulls/4794

 

Reviewed-by: Lu Jialin <lujialin4@huawei.com>
Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com>