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/Makefile b/Makefile
index beb0237..43ff8d2 100644
--- a/Makefile
+++ b/Makefile
@@ -734,12 +734,6 @@
                 $(eval $(call add_define,PRELOADED_BL33_BASE))
         endif
 endif
-# Define the AARCH32/AARCH64 flag based on the ARCH flag
-ifeq (${ARCH},aarch32)
-        $(eval $(call add_define,AARCH32))
-else
-        $(eval $(call add_define,AARCH64))
-endif
 
 # Define the DYN_DISABLE_AUTH flag only if set.
 ifeq (${DYN_DISABLE_AUTH},1)
@@ -771,6 +765,12 @@
 endif
 # __ASSEMBLY__ is deprecated in favor of the compiler-builtin __ASSEMBLER__.
 ASFLAGS	+= -D__ASSEMBLY__
+# AARCH32/AARCH64 macros are deprecated in favor of the compiler-builtin __aarch64__.
+ifeq (${ARCH},aarch32)
+        $(eval $(call add_define,AARCH32))
+else
+        $(eval $(call add_define,AARCH64))
+endif
 endif # !ERROR_DEPRECATED
 
 $(eval $(call MAKE_LIB_DIRS))