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

llvm-svn: 152997
diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.h b/llvm/lib/Target/PowerPC/PPCISelLowering.h
index 3534e9c..2e046c4 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.h
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.h
@@ -15,10 +15,10 @@
 #ifndef LLVM_TARGET_POWERPC_PPC32ISELLOWERING_H
 #define LLVM_TARGET_POWERPC_PPC32ISELLOWERING_H
 
-#include "llvm/Target/TargetLowering.h"
-#include "llvm/CodeGen/SelectionDAG.h"
 #include "PPC.h"
 #include "PPCSubtarget.h"
+#include "llvm/Target/TargetLowering.h"
+#include "llvm/CodeGen/SelectionDAG.h"
 
 namespace llvm {
   namespace PPCISD {