Reorder includes in Target backends to following coding standards. Remove some superfluous forward declarations.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@152997 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/PTX/PTXAsmPrinter.cpp b/lib/Target/PTX/PTXAsmPrinter.cpp
index 58ac5f2..0b6ac7b 100644
--- a/lib/Target/PTX/PTXAsmPrinter.cpp
+++ b/lib/Target/PTX/PTXAsmPrinter.cpp
@@ -14,8 +14,8 @@
 
 #define DEBUG_TYPE "ptx-asm-printer"
 
-#include "PTX.h"
 #include "PTXAsmPrinter.h"
+#include "PTX.h"
 #include "PTXMachineFunctionInfo.h"
 #include "PTXParamManager.h"
 #include "PTXRegisterInfo.h"