AMDGPU: address -Winconsistent-missing-override

Add missing override.  NFC.

llvm-svn: 248652
diff --git a/llvm/lib/Target/AMDGPU/AMDGPUHSATargetObjectFile.h b/llvm/lib/Target/AMDGPU/AMDGPUHSATargetObjectFile.h
index d13aba5..e1aca67 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUHSATargetObjectFile.h
+++ b/llvm/lib/Target/AMDGPU/AMDGPUHSATargetObjectFile.h
@@ -23,7 +23,7 @@
 
 class AMDGPUHSATargetObjectFile final : public TargetLoweringObjectFileELF {
 public:
-  void Initialize(MCContext &Ctx, const TargetMachine &TM);
+  void Initialize(MCContext &Ctx, const TargetMachine &TM) override;
 
   MCSection *SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
                                     Mangler &Mang,