Add support for AMDGPU 0.9

[pxl-th]

• Add support for AMDGPU 0.9.
• Remove MIOpen softmax wrappers (rely on pure Julia implementations) as they have issues: Remove MIOpen softmax & batchnorm JuliaGPU/AMDGPU.jl#630

PR Checklist

• Tests are added
• Documentation, if applicable

[darsnack]

Should we switch back to MIOpen implementations once the upstream issue is fixed? If so, can you create an issue here to track it?

[pxl-th]

Thanks for merging! Yes, if they fix it we can add it back. Although I'd prefer to have more Julia-native kernels :)
Can we also tag a release for NNlib? I'd like to update Flux as well next.