[llvm] [AMDGPU] Extend wide VGPR copy expansion to 96-bit copies (PR #214561)

[Matt Arsenault via llvm-commits]

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arsenm wrote:

Take the register class from the instruction you are going to emit's operand descriptor. i.e. TII->getRegClass(getDesc(V_MOV_B64), 1)

https://github.com/llvm/llvm-project/pull/214561