[llvm-mca] Use llvm::make_unique in a few places. NFC

Also, clang-format a couple of DEBUG functions.

llvm-svn: 327978
diff --git a/llvm/tools/llvm-mca/InstrBuilder.h b/llvm/tools/llvm-mca/InstrBuilder.h
index a26b846..d31ccef 100644
--- a/llvm/tools/llvm-mca/InstrBuilder.h
+++ b/llvm/tools/llvm-mca/InstrBuilder.h
@@ -53,7 +53,8 @@
 
   const InstrDesc &getOrCreateInstrDesc(const llvm::MCInst &MCI);
 
-  Instruction *createInstruction(unsigned Idx, const llvm::MCInst &MCI);
+  std::unique_ptr<Instruction> createInstruction(unsigned Idx,
+                                                 const llvm::MCInst &MCI);
 };
 } // namespace mca