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/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