[llvm] [X86] Resolve FIXME: Copy kill flag for eflags (PR #82411)

[Simon Pilgrim via llvm-commits]

https://github.com/RKSimon commented:

Do you think we should we consider altering the findRegisterDefOperandIdx/findRegisterDefOperand argument order and require the TRI pointer to help avoid this in the future?

https://github.com/llvm/llvm-project/pull/82411