[llvm] [Mips] Add the missing judgment when processing function handleMFLOSlot (PR #121463)

[YunQiang Su via llvm-commits]

wzssyqa wrote:

I guess that there may be some other problem: why this patch can effects MIPSr2?
I guess that the default port of FreeBSD is r2？

https://github.com/llvm/llvm-project/pull/121463