X86MCTargetDesc.h - replace FormattedStream.h include with forward declaration. NFC.

llvm/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.h

@@ -14,10 +14,11 @@
 #define LLVM_LIB_TARGET_X86_MCTARGETDESC_X86MCTARGETDESC_H
 
 #include "llvm/Support/DataTypes.h"
-#include "llvm/Support/FormattedStream.h"
+#include <memory>
 #include <string>
 
 namespace llvm {
+class formatted_raw_ostream;
 class MCAsmBackend;
 class MCCodeEmitter;
 class MCContext;