[AMDGPU] Create a TargetInfo header.  NFC

Move the declarations of getThe<Name>Target() functions into a new header in
TargetInfo and make users of these functions include this new header.
This fixes a layering problem.

llvm-svn: 360713
diff --git a/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp b/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp
index e124113..8687759 100644
--- a/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp
+++ b/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp
@@ -12,6 +12,7 @@
 #include "MCTargetDesc/AMDGPUTargetStreamer.h"
 #include "SIDefines.h"
 #include "SIInstrInfo.h"
+#include "TargetInfo/AMDGPUTargetInfo.h"
 #include "Utils/AMDGPUAsmUtils.h"
 #include "Utils/AMDGPUBaseInfo.h"
 #include "Utils/AMDKernelCodeTUtils.h"