[llvm] [X86] X86LegalizerInfo - use LegalFor instead if LegalIf for simple ISA/test pairs (PR #144675)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

No release notes are required - as you explained this is a refactoring/cleanup patch, and shouldn't affect codegen.

https://github.com/llvm/llvm-project/pull/144675