Add ability to enable/disable MIOpen at runtime (#33118)
Summary:
1. Set `torch._C.has_cudnn` to `True` for ROCm
2. Make MIOpen invocations respect value of `cudnn_enabled` or `at::globalContext().userEnabledCuDNN()`
3. `torch/backends/cudnn/__init__.py`: Add hip-specific changes (use "hide whitespace changes" option to view simpler diff)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/33118
Differential Revision: D19977719
Pulled By: bddppq
fbshipit-source-id: 64d4dd1d78afcf96201360d85b8be5950f96dfad
