batman-adv: Use "__attribute__" shortcut macros

Linux 2.6.21 defines different macros for __attribute__ which are also
used inside batman-adv. The next version of checkpatch.pl warns about
the usage of __attribute__((packed))).

Linux 2.6.33 defines an extra macro __always_unused which is used to
assist source code analyzers and can be used to removed the last
existing __attribute__ inside the source code.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
diff --git a/net/batman-adv/main.h b/net/batman-adv/main.h
index d4d9926..65106fb 100644
--- a/net/batman-adv/main.h
+++ b/net/batman-adv/main.h
@@ -151,9 +151,9 @@
 	}							\
 	while (0)
 #else /* !CONFIG_BATMAN_ADV_DEBUG */
-static inline void bat_dbg(char type __attribute__((unused)),
-			   struct bat_priv *bat_priv __attribute__((unused)),
-			   char *fmt __attribute__((unused)), ...)
+static inline void bat_dbg(char type __always_unused,
+			   struct bat_priv *bat_priv __always_unused,
+			   char *fmt __always_unused, ...)
 {
 }
 #endif