[llvm] MachinePipeliner: Pass instruction to findLoopIncrementValue (PR #219966)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> LGTM. Are you planning to remove getParent from MachineOperand?

I aspire to but at the moment it seems it requires a lot more use list changes than seems feasible anytime soon 

https://github.com/llvm/llvm-project/pull/219966