Revert "TargetMachine: Merge TargetMachine and LLVMTargetMachine"

Reverting to investigate layering effects of MCJIT not linking
libCodeGen but using TargetMachine::getNameWithPrefix() breaking the
lldb bots.

This reverts commit r315633.

llvm-svn: 315637
diff --git a/llvm/lib/Target/AVR/AVRTargetMachine.h b/llvm/lib/Target/AVR/AVRTargetMachine.h
index 123ee31..ffcf435 100644
--- a/llvm/lib/Target/AVR/AVRTargetMachine.h
+++ b/llvm/lib/Target/AVR/AVRTargetMachine.h
@@ -26,11 +26,12 @@
 namespace llvm {
 
 /// A generic AVR implementation.
-class AVRTargetMachine : public TargetMachine {
+class AVRTargetMachine : public LLVMTargetMachine {
 public:
   AVRTargetMachine(const Target &T, const Triple &TT, StringRef CPU,
                    StringRef FS, const TargetOptions &Options,
-                   Optional<Reloc::Model> RM, Optional<CodeModel::Model> CM,
+                   Optional<Reloc::Model> RM,
+                   Optional<CodeModel::Model> CM,
                    CodeGenOpt::Level OL, bool JIT);
 
   const AVRSubtarget *getSubtargetImpl() const;