[llvm] [AMDGPU]: Add regbank legalize rules for amdgcn exp2 intrinsics (PR #191953)

[Jasmine Tang via llvm-commits]

================

----------------
badumbatish wrote:

yep, added, there's a lot more CHECK lines but i'm not sure if i should use the filter-out args like how `llvm/test/CodeGen/AMDGPU/llvm.amdgcn.fdot2.ll` is doing it to help reduce the duplication

https://github.com/llvm/llvm-project/pull/191953