[ARM] 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: 360718
diff --git a/llvm/lib/Target/ARM/ARMAsmPrinter.cpp b/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
index 67f026f..239b95f 100644
--- a/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
+++ b/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
@@ -20,6 +20,7 @@
 #include "MCTargetDesc/ARMAddressingModes.h"
 #include "MCTargetDesc/ARMInstPrinter.h"
 #include "MCTargetDesc/ARMMCExpr.h"
+#include "TargetInfo/ARMTargetInfo.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/BinaryFormat/COFF.h"