[AMDGPU][SIFoldOperands] Fix OR -1 fold (#189655)
In SIFoldOperands, folding `or x, -1` to `v_mov_b32 -1` removed
`Src1Idx`, which is incorrect because `-1` is in `Src0Idx` (after
canonicalization).
Closes https://github.com/llvm/llvm-project/issues/189677.
