DebugInfo: Remove unnecessary zero-size check

DebugInfo: Remove unnecessary zero-size check

This seems excessive - switching section isn't expensive (or if it is
we're already being wasteful, since we emitted the debug_loc section
symbol earlier anyway) and otherwise there's no work that happens in
this function when the list is empty.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204696 91177308-0d34-0410-b5e6-96231b3b80d8