[llvm] [AMDGPU] Restrict DPP combine from performing bad transformations when handling certain REV insts that use Src1 as the DPP operand (PR #216835)

[Domenic Nutile via llvm-commits]

saxlungs wrote:

> Hi @saxlungs , the `dpp_combine_rev_opcode.ll` test gets failed on the expensive check builders after these changes:

Looking into it now, thanks for the heads up

https://github.com/llvm/llvm-project/pull/216835