!3730 ARM: spectre-v2: turn off the mitigation via boot cmdline param

Merge Pull Request from: @ci-robot 
 
PR sync from: Yi Yang <yiyang13@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/BTBMZTVNYVTTIA2CV6IJC744DIQ3BS73/ 
 
https://gitee.com/openeuler/kernel/issues/I8SE4Y 
 
Link:https://gitee.com/openeuler/kernel/pulls/3730

 

Reviewed-by: Zhang Jianhua <chris.zjh@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>