AMDGPU: Fix missing C++ mode comment

llvm-svn: 335160
diff --git a/llvm/lib/Target/AMDGPU/AMDGPULibFunc.h b/llvm/lib/Target/AMDGPU/AMDGPULibFunc.h
index 5405bc6..fe06238 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPULibFunc.h
+++ b/llvm/lib/Target/AMDGPU/AMDGPULibFunc.h
@@ -1,4 +1,4 @@
-//===-- AMDGPULibFunc.h ---------------------------------------------------===//
+//===-- AMDGPULibFunc.h ----------------------------------------*- C++ -*--===//
 //
 //                     The LLVM Compiler Infrastructure
 //