batman-adv: Return error codes instead of -1 on failures

Signed-off-by: Sven Eckelmann <sven@narfation.org>
diff --git a/net/batman-adv/bat_iv_ogm.c b/net/batman-adv/bat_iv_ogm.c
index 56b6d78..896287e 100644
--- a/net/batman-adv/bat_iv_ogm.c
+++ b/net/batman-adv/bat_iv_ogm.c
@@ -60,7 +60,7 @@
 {
 	struct batman_ogm_packet *batman_ogm_packet;
 	uint32_t random_seqno;
-	int res = -1;
+	int res = -ENOMEM;
 
 	/* randomize initial seqno to avoid collision */
 	get_random_bytes(&random_seqno, sizeof(random_seqno));