[llvm] [AArch64][NFC] Hoist TRI definition on AArch64InstrInfo::copyPhysReg (PR #162826)

[Benjamin Maxwell via llvm-commits]

https://github.com/MacDue commented:

I think all `const TargetRegisterInfo *TRI = &getRegisterInfo();` in this function can be replaced with `RI.` (which reuses the existing member variable). 

https://github.com/llvm/llvm-project/pull/162826