batman-adv: add bridge loop avoidance compile option

The define CONFIG_BATMAN_ADV_BLA switches the bridge loop avoidance
on - skip it, and the bridge loop avoidance is not compiled in.

This is useful if binary size should be saved or the feature is
not needed.

Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Antonio Quartulli <ordex@autistici.org>
diff --git a/net/batman-adv/Makefile b/net/batman-adv/Makefile
index 94b67fd..6d5c194 100644
--- a/net/batman-adv/Makefile
+++ b/net/batman-adv/Makefile
@@ -23,7 +23,7 @@
 batman-adv-y += bat_iv_ogm.o
 batman-adv-y += bat_sysfs.o
 batman-adv-y += bitarray.o
-batman-adv-y += bridge_loop_avoidance.o
+batman-adv-$(CONFIG_BATMAN_ADV_BLA) += bridge_loop_avoidance.o
 batman-adv-y += gateway_client.o
 batman-adv-y += gateway_common.o
 batman-adv-y += hard-interface.o