Remove direct usage of __attribute__((foo))

Migrate all direct usage of __attribute__ to usage of their
corresponding macros from cdefs.h.
e.g.:
 - __attribute__((unused)) -> __unused

Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
diff --git a/include/bl31/runtime_svc.h b/include/bl31/runtime_svc.h
index 87f2dd2..03f906e 100644
--- a/include/bl31/runtime_svc.h
+++ b/include/bl31/runtime_svc.h
@@ -88,7 +88,7 @@
  */
 #define DECLARE_RT_SVC(_name, _start, _end, _type, _setup, _smch) \
 	static const rt_svc_desc_t __svc_desc_ ## _name \
-		__attribute__ ((section("rt_svc_descs"), used)) = { \
+		__section("rt_svc_descs") __used = { \
 			.start_oen = _start, \
 			.end_oen = _end, \
 			.call_type = _type, \
diff --git a/include/drivers/auth/img_parser_mod.h b/include/drivers/auth/img_parser_mod.h
index d80e0fb..79d7d79 100644
--- a/include/drivers/auth/img_parser_mod.h
+++ b/include/drivers/auth/img_parser_mod.h
@@ -77,7 +77,7 @@
 /* Macro to register an image parser library */
 #define REGISTER_IMG_PARSER_LIB(_type, _name, _init, _check_int, _get_param) \
 	static const img_parser_lib_desc_t __img_parser_lib_desc_##_type \
-	__attribute__ ((section(".img_parser_lib_descs"), used)) = { \
+	__section(".img_parser_lib_descs") __used = { \
 		.img_type = _type, \
 		.name = _name, \
 		.init = _init, \
diff --git a/include/lib/bakery_lock.h b/include/lib/bakery_lock.h
index 86adb9c..8a53891 100644
--- a/include/lib/bakery_lock.h
+++ b/include/lib/bakery_lock.h
@@ -100,8 +100,7 @@
 void bakery_lock_get(bakery_lock_t *bakery);
 void bakery_lock_release(bakery_lock_t *bakery);
 
-#define DEFINE_BAKERY_LOCK(_name) bakery_lock_t _name \
-			__attribute__ ((section("bakery_lock")))
+#define DEFINE_BAKERY_LOCK(_name) bakery_lock_t _name __section("bakery_lock")
 
 #define DECLARE_BAKERY_LOCK(_name) extern bakery_lock_t _name
 
diff --git a/include/lib/cassert.h b/include/lib/cassert.h
index e8089cb..00ee4d5 100644
--- a/include/lib/cassert.h
+++ b/include/lib/cassert.h
@@ -40,6 +40,6 @@
  * compiler warning.
  ******************************************************************************/
 #define CASSERT(cond, msg)	\
-	typedef char msg[(cond) ? 1 : -1] __attribute__((unused))
+	typedef char msg[(cond) ? 1 : -1] __unused
 
 #endif /* __CASSERT_H__ */