[clang] [AMDGPU] const-fold imm operands of amdgcn_update_dpp intrinsic (PR #71139)

[Matt Arsenault via cfe-commits]

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

Could probably golf this down for more sharing with the default path but this is a start 

https://github.com/llvm/llvm-project/pull/71139