net/icmp: use break instead of return in icmp_findconn

Replace return with break inside the loop in icmp_findconn() to
ensure any post-loop cleanup logic is properly executed before
returning.

Signed-off-by: zhanghongyu <zhanghongyu@xiaomi.com>

net/icmp/icmp_conn.c

@@ -241,7 +241,7 @@ FAR struct icmp_conn_s *icmp_findconn(FAR struct net_driver_s *dev,
     {
       if (conn->id == id && conn->dev == dev)
         {
-          return conn;
+          break;
         }
     }