!165 ascend agent smmu: an implementation of ARM SMMUv3 ATOS feature

Merge Pull Request from: @yezengruan 
 
To support HCCS bus using in Ascend series accelerators, the SMMU ATOS
(a software-accessible Address Translation Operations facility) feature
is enabled for a special SMMU aka Agent SMMU in the Ascend accelerator.

In the VM scenario, the hypervisor creates Stage1 page table for the
Agent SMMU. The Agent SMMU provides an interface for components in
accelerator to translate addresses from IPA to PA. This allows the
components to DMA on the HCCS bus using PA.

The origin SMMU ATOS feature only support translation of only a single
group of addresses at a time. Ascend Agent SMMUs use the IMPLEMENTATION
DEFINED region to implement translation of max 32 groups of addresses at
the same time which can greatly improve the efficiency. 
 
Link:https://gitee.com/openeuler/kernel/pulls/165

 
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Reviewed-by: Kevin Zhu <zhukeqian1@huawei.com>
Reviewed-by: Zheng Zengkai <zhengzengkai@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>