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/make_helpers/build_macros.mk b/make_helpers/build_macros.mk
index 4a9677b..b89d87e 100644
--- a/make_helpers/build_macros.mk
+++ b/make_helpers/build_macros.mk
@@ -273,7 +273,7 @@
 
 $(1): $(2) $(filter-out %.d,$(MAKEFILE_LIST)) | bl$(3)_dirs
 	$$(ECHO) "  PP      $$<"
-	$$(Q)$$(CPP) $$(CPPFLAGS) -P -x assembler-with-cpp -D__LINKER__ $(MAKE_DEP) -D$(IMAGE) -o $$@ $$<
+	$$(Q)$$(CPP) $$(CPPFLAGS) $(TF_CFLAGS_$(ARCH)) -P -x assembler-with-cpp -D__LINKER__ $(MAKE_DEP) -D$(IMAGE) -o $$@ $$<
 
 -include $(DEP)