[qca-nss-ecm] Fixed a kernel panic due to double free

While running the stability test a kernel panic observed
in Multicast path after couples of hours. The root cause is
a double free in multicast process function.

Change-Id: I23482be039c1e412b5e4acd52b4a8e5f29aa58d6
Signed-off-by: Shyam Sunder <ssunde@codeaurora.org>
diff --git a/ecm_interface.c b/ecm_interface.c
index 193fabb..a59fe19 100644
--- a/ecm_interface.c
+++ b/ecm_interface.c
@@ -3164,7 +3164,7 @@
 		dev_put(mc_br_slave_dev);
 	}
 
-	return ii_cnt;
+	return valid_if;
 }
 EXPORT_SYMBOL(ecm_interface_multicast_heirarchy_construct_bridged);