Switch AARCH32/AARCH64 to __aarch64__

NOTE: AARCH32/AARCH64 macros are now deprecated in favor of __aarch64__.

All common C compilers pre-define the same macros to signal which
architecture the code is being compiled for: __arm__ for AArch32 (or
earlier versions) and __aarch64__ for AArch64. There's no need for TF-A
to define its own custom macros for this. In order to unify code with
the export headers (which use __aarch64__ to avoid another dependency),
let's deprecate the AARCH32 and AARCH64 macros and switch the code base
over to the pre-defined standard macro. (Since it is somewhat
unintuitive that __arm__ only means AArch32, let's standardize on only
using __aarch64__.)

Change-Id: Ic77de4b052297d77f38fc95f95f65a8ee70cf200
Signed-off-by: Julius Werner <jwerner@chromium.org>
diff --git a/include/plat/common/common_def.h b/include/plat/common/common_def.h
index 66c88ba..14ae603 100644
--- a/include/plat/common/common_def.h
+++ b/include/plat/common/common_def.h
@@ -20,13 +20,13 @@
 /*
  * Platform binary types for linking
  */
-#ifdef AARCH32
-#define PLATFORM_LINKER_FORMAT          "elf32-littlearm"
-#define PLATFORM_LINKER_ARCH            arm
-#else
+#ifdef __aarch64__
 #define PLATFORM_LINKER_FORMAT          "elf64-littleaarch64"
 #define PLATFORM_LINKER_ARCH            aarch64
-#endif /* AARCH32 */
+#else
+#define PLATFORM_LINKER_FORMAT          "elf32-littlearm"
+#define PLATFORM_LINKER_ARCH            arm
+#endif /* __aarch64__ */
 
 /*
  * Generic platform constants