Add device range helper and remove sm86 specific check for memory efficient attention (#102985)
# Summary
Since we have upstreamed the latest changes of memory efficient attetnion we can remove the sm86/sm89 specific check. All head_sizes (assuming correctly alignment) should work for sm86 and sm89 size and don't have a max capability.
If head_size > 96 there will be a big drop in performance but should not error and still maintain memory savings by not materializing attention weights.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/102985
Approved by: https://github.com/cpuhrsch
