[llvm] [AMDGPU] Stop adding implicit def of superreg in copyPhysReg (PR #125255)

[Pravin Jagtap via llvm-commits]

pravinjagtap wrote:

This is surprising!!

During spill expansion, source tuple is marked as implicit-def not the dest.

Refer:
https://github.com/llvm/llvm-project/blob/main/llvm/test/CodeGen/AMDGPU/pei-build-av-spill.mir 

https://github.com/llvm/llvm-project/blob/646d352ab0d0a9cfafa3f2c9c415b5773834ad5b/llvm/lib/Target/AMDGPU/SIRegisterInfo.cpp#L1818C28-L1820C56  

https://github.com/llvm/llvm-project/pull/125255