Slightly saner handling of thumb branches.

The generic infrastructure already did a lot of work to decide if the
fixup value is know or not. It doesn't make sense to reimplement a very
basic case: same fragment.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@252090 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed