[AMDGPU] Allow selection of BITOP3 for some 2 opcodes and B32 cases (#122267)
This came up in downstream static analysis - as a dead code.
Admittedly, it depends on what the intention was when checking for [`if
(NumOpcodes == 2 &&
IsB32)`](https://github.com/llvm/llvm-project/blob/main/llvm/lib/Target/AMDGPU/AMDGPUInstructionSelector.cpp#L3792C3-L3792C32)
and I took a guess that for certain cases the selection should take
place.
If that's incorrect, that whole if statement can be removed, as it is
after a check for: [`if (NumOpcodes <
4)`](https://github.com/llvm/llvm-project/blob/main/llvm/lib/Target/AMDGPU/AMDGPUInstructionSelector.cpp#L3788)