[llvm] [AMDGPU] Allow lane-op lowering for some illegal types (PR #114887)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> Clang can produce intrinsic with char argument out of builtin. Will be able after #115090.

It makes sense to overload and accept the types that will naturally be passed in registers, but I don't think we want to permit cases where there's going to be an implicit cast. Maybe it's OK for i8, but i1 is special and we probably shouldn't treat it like an arbitrary VGPR value

https://github.com/llvm/llvm-project/pull/114887