!6966 speakup: Avoid crash on very long word

Merge Pull Request from: @ci-robot 
 
PR sync from: Zhang Xiaoxu <zhangxiaoxu5@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/4QGXR5FQAXO7UHHNBKEZMRE4MGJH54GS/ 
 
https://gitee.com/src-openeuler/kernel/issues/I9L5L5 
 
Link:https://gitee.com/openeuler/kernel/pulls/6966

 

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