Add AMD ROCm support, I have successfully run on Radeon VII with ROCm !

[acai66]

Describe the feature
I have modified some .cu files, so AMD ROCm works fine, but i don't know that's correct or not.
I really hope this feature will become official support.

Motivation
I hope to get more extensive support and application through this feature .

Related resources
I have forked a copy of mmdetection in my repo, and i have successfully run some models on my AMD Radeon VII graphics card, this is a demo.

Additional context
Here is my commit, i know it's not perfect.

Installion:

Training and testing:

Envs:

[hellock]

Thanks for your efforts! We will migrate to mmcv.ops and you may create a PR in mmcv.

[acai66]

Thanks for your efforts! We will migrate to mmcv.ops and you may create a PR in mmcv.

我已经尝试发起了PR, #3235, 这个只在我的A卡机器上做了部分测试，由于没有Nvidia显卡，就没能测试CUDA，一般而言，我的提交是不会影响 nvcc 编译的。

[ZwwWayne]

Supported in open-mmlab/mmcv#1022. You may have a try and feel free to create a new issue if you meet any unexpected results