COFF: Fix bad #includes.

Writer.h is intended to be included only by Writer.cpp and Driver.cpp.
Use of the header in other files are bad.

llvm-svn: 244106
diff --git a/lld/COFF/InputFiles.cpp b/lld/COFF/InputFiles.cpp
index 9214af6..215271c 100644
--- a/lld/COFF/InputFiles.cpp
+++ b/lld/COFF/InputFiles.cpp
@@ -10,7 +10,7 @@
 #include "Chunks.h"
 #include "Error.h"
 #include "InputFiles.h"
-#include "Writer.h"
+#include "Symbols.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/LTO/LTOModule.h"
 #include "llvm/Object/COFF.h"