[ROCM] MIOpen contrib for convolution kernels (#722)

* fist working miopen support

* do FindFwdAlgo during build time

* fix lint

* update doc string

* import topi after checking if rocm is enabled

* add miopen namespace

* fixed descriptor overwrite bug

* add use_miopen option

* fix lint

* better miopen option handling

* fix typo

* fix options handling