[llvm] [AMDGPU] Switch V_CNDMASK operands to shrink it into VOP2 (PR #135162)

[Mirko Brkušanin via llvm-commits]

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+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
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mbrkusanin wrote:

Also add examples with source modifiers and maybe a negative case (both because of source modifiers and immediate for src1)

https://github.com/llvm/llvm-project/pull/135162