!629 arm64: Add initial support for FEAT_WFxT

Merge Pull Request from: @did-you-collect-the-wool-today 
 
The ARMv8.7 WFxT feature is a new take on the good old WFI/WFE
instructions as they behave the same way, only taking an extra timeout
parameter.

This small series aims at adding the minimal support for this feature,
enabling it for both the kernel and KVM. 
 
Link:https://gitee.com/openeuler/kernel/pulls/629

 

Reviewed-by: Zenghui Yu <yuzenghui@huawei.com>
Reviewed-by: Jialin Zhang <zhangjialin11@huawei.com>
Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com>