[llvm] [Mips] Fix fixpoint iteration in MipsBranchExpansion (PR #223900)

[Ying Huang via llvm-commits]

yingopq wrote:

> Instead of checking all the possible changes, would it also work to just have handlePossibleLongBranch() run last? That's the only one that depends on offsets / instruction sizes, right?

I adjusted the order this way because if any of the four changes, function `handlePossibleLongBranch` must be run again to check if expansion is required. The `while` loop will stop only when no further changes occur.

https://github.com/llvm/llvm-project/pull/223900