batman-adv: properly convert flag into a boolean value

In order to properly convert a bitwise AND to a boolean value, the whole
expression must be prepended by "!!".

Signed-off-by: Antonio Quartulli <ordex@autistici.org>

net/batman-adv/translation-table.c

@@ -2420,7 +2420,7 @@ bool batadv_tt_global_client_is_roaming(struct batadv_priv *bat_priv,
 	if (!tt_global_entry)
 		goto out;
 
-	ret = tt_global_entry->common.flags & BATADV_TT_CLIENT_ROAM;
+	ret = !!(tt_global_entry->common.flags & BATADV_TT_CLIENT_ROAM);
 	batadv_tt_global_entry_free_ref(tt_global_entry);
 out:
 	return ret;