!6852 serial/pmac_zilog: Remove flawed mitigation for rx irq flood

Merge Pull Request from: @ci-robot 
 
PR sync from: Yi Yang <yiyang13@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/LYNHAH4HP6AONSOXIIFNOIE5OIGGW7JA/ 
 
https://gitee.com/src-openeuler/kernel/issues/I9L5KR 
 
Link:https://gitee.com/openeuler/kernel/pulls/6852

 

Reviewed-by: Liu YongQiang <liuyongqiang13@huawei.com>
Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com>