[NVPTX] Remove unused forward declarations. NFC.

llvm/lib/Target/NVPTX/MCTargetDesc/NVPTXMCAsmInfo.h

@@ -16,7 +16,6 @@
 #include "llvm/MC/MCAsmInfo.h"
 
 namespace llvm {
-class Target;
 class Triple;
 
 class NVPTXMCAsmInfo : public MCAsmInfo {

llvm/lib/Target/NVPTX/MCTargetDesc/NVPTXMCTargetDesc.h

@@ -15,11 +15,6 @@
 
 #include <stdint.h>
 
-namespace llvm {
-class Target;
-
-} // End llvm namespace
-
 // Defines symbolic names for PTX registers.
 #define GET_REGINFO_ENUM
 #include "NVPTXGenRegisterInfo.inc"

llvm/lib/Target/NVPTX/NVPTX.h

@@ -21,7 +21,6 @@ namespace llvm {
 class NVPTXTargetMachine;
 class FunctionPass;
 class MachineFunctionPass;
-class formatted_raw_ostream;
 
 namespace NVPTXCC {
 enum CondCodes {

llvm/lib/Target/NVPTX/NVPTXFrameLowering.h

@@ -16,7 +16,7 @@
 #include "llvm/CodeGen/TargetFrameLowering.h"
 
 namespace llvm {
-class NVPTXSubtarget;
+
 class NVPTXFrameLowering : public TargetFrameLowering {
 public:
   explicit NVPTXFrameLowering();