Fix accidental fallthrough in DebugLocEntry::hasSameValueOrLocation

No test case (this would invoke UB by examining uninitialized members,
etc, at best - and this code is apparently untested anyway - I'm about
to fix that)

Code review feedback from Adrian Prantl on r205360.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205367 91177308-0d34-0410-b5e6-96231b3b80d8