[llvm] Reland "[NVPTX] Legalize aext-load to zext-load to expose more DAG combines" (PR #155063)

[Joseph Huber via llvm-commits]

https://github.com/jhuber6 approved this pull request.

Seems fine, were you able to test the libc stuff locally?

https://github.com/llvm/llvm-project/pull/155063