[llvm] [X86][SelectionDAG] Fix the Gather's base and index by modifying the Scale value (PR #134979)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

cheers @rohitaggarwal007 - I've pushed your test coverage to trunk inside masked_gather_scatter.ll - so you should be able to merge (and remove gatherBaseIndexFix.ll its now superfluous) - my test patch now shows the current diff for your tests

https://github.com/llvm/llvm-project/pull/134979