Sink DwarfUnit::SectionSym into DwarfCompileUnit as it's only needed/used there.

llvm-svn: 221062
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index a4f5e55..bbac479 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -2151,8 +2151,7 @@
   NewTU.setTypeSignature(Signature);
 
   if (useSplitDwarf())
-    NewTU.initSection(Asm->getObjFileLowering().getDwarfTypesDWOSection(),
-                      DwarfTypesDWOSectionSym);
+    NewTU.initSection(Asm->getObjFileLowering().getDwarfTypesDWOSection());
   else {
     CU.applyStmtList(UnitDie);
     NewTU.initSection(