net/rpmsg: add err handle when rpmsg_socket_unbind called

After waiting, it is necessary to check if the connection
has been disconnected

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

net/rpmsg/rpmsg_sockif.c

@@ -778,6 +778,10 @@ static int rpmsg_socket_connect_internal(FAR struct socket *psock)
 
       ret = net_sem_timedwait(&conn->sendsem,
                               _SO_TIMEOUT(conn->sconn.s_sndtimeo));
+      if (!conn->ept.rdev || conn->unbind)
+        {
+          ret = -ECONNRESET;
+        }
 
       if (ret < 0)
         {