[llvm] [AMDGPU] Move INIT_EXEC lowering from SILowerControlFlow to SIWholeQuadMode (PR #94452)

[Carl Ritson via llvm-commits]

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

LGTM

This is a straight forward relocation of the existing code.

https://github.com/llvm/llvm-project/pull/94452