[llvm] [NVPTX] prefetch.tensormap pattern rewriter fix (PR #159253)

[Giacomo Castiglioni via llvm-commits]

castigli wrote:

Thanks @abhilash1910 for the patch! 
I can confirm that this resolves the issue raised in #156830 (since there is no CI for sm_90!).

https://github.com/llvm/llvm-project/pull/159253