[lld] Include reference kind in cycle detector debug output

This restores the debug output to how it was before r197727 broke it. This
went undetected because the corresponding test was never run due to broken
feature detection.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@202079 91177308-0d34-0410-b5e6-96231b3b80d8