[llvm] Stop including llvm/ADT/StringMap.h (NFC)

Identified misc-include-cleaner.

Author: kazutakahirata

llvm/lib/Target/AMDGPU/GCNCreateVOPD.cpp

@@ -25,7 +25,6 @@
 #include "Utils/AMDGPUBaseInfo.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/Statistic.h"
-#include "llvm/ADT/StringMap.h"
 #include "llvm/CodeGen/MachineBasicBlock.h"
 #include "llvm/CodeGen/MachineInstr.h"
 #include "llvm/CodeGen/MachineOperand.h"

llvm/lib/Target/NVPTX/NVVMReflect.cpp

@@ -20,7 +20,6 @@
 
 #include "NVPTX.h"
 #include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/StringMap.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Function.h"

llvm/lib/Transforms/IPO/SampleContextTracker.cpp

@@ -11,7 +11,6 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Transforms/IPO/SampleContextTracker.h"
-#include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/InstrTypes.h"