Fix previous commit and fully remove variable.

llvm-svn: 195076
diff --git a/llvm/lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp b/llvm/lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp
index 16f65b4..250b0af 100644
--- a/llvm/lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp
+++ b/llvm/lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp
@@ -23,8 +23,7 @@
 // pin vtable to this file
 void MipsTargetStreamer::anchor() {}
 
-MipsTargetAsmStreamer::MipsTargetAsmStreamer(formatted_raw_ostream &OS)
-    : OS(OS) {}
+MipsTargetAsmStreamer::MipsTargetAsmStreamer() {}
 
 void MipsTargetAsmStreamer::emitMipsHackELFFlags(unsigned Flags) {
   return;