[ROCm] Enable double __shfl_down (#34103)
Summary:
This allows us to enable some double-based pdist tests running into accrued error from casting down to float previously.
Addresses https://github.com/pytorch/pytorch/issues/33128
Pull Request resolved: https://github.com/pytorch/pytorch/pull/34103
Differential Revision: D20343279
Pulled By: ezyang
fbshipit-source-id: a2da768259fab34ef326976283b7a15bebbbb979
