[llvm] [AMDGPU][MC] Adding symbolic name for the constant 1 over 2*pi (PR #160617)

[Matt Arsenault via llvm-commits]

arsenm wrote:

If SP3 doesn't do this, I don't think we should introduce it. I certainly don't think we should be emitting it even if we did parse it 

https://github.com/llvm/llvm-project/pull/160617