[llvm] [DAGCombiner] Share byte provider steps with AMDGPU target (PR #221959)

[Shilei Tian via llvm-commits]

================
@@ -9734,24 +9733,19 @@ calculateByteProvider(SDValue Op, unsigned Index, unsigned Depth,
     return std::nullopt;
   unsigned ByteWidth = BitWidth / 8;
----------------
shiltian wrote:

`[[maybe_used]]`

https://github.com/llvm/llvm-project/pull/221959