[llvm] [AMDGPU] Do not fold COPY with implicit operands (PR #136003)

[Carl Ritson via llvm-commits]

https://github.com/perlfu commented:

Narrowing the operand fold is obviously safe.
The test changes suggest minimal fallout, but I wonder how that scales to actual code bases?
That said, I don't immediately see better solution *right now* for this problem.

https://github.com/llvm/llvm-project/pull/136003