[llvm] [Codegen] Remove redundant pseudo mov instruction (PR #139716)

[Simon Pilgrim via llvm-commits]

https://github.com/RKSimon requested changes to this pull request.

@rohitaggarwal007 please can merge against trunk - I've tried to clean up some tests to reduce the superfluous x86 diffs

https://github.com/llvm/llvm-project/pull/139716