ser-tcp.c: Small signed->unsigned cleanup.

ser-tcp.c: Small signed->unsigned cleanup.

The "set tcp connect-timeout" variable is unsigned:

  /* Timeout period for connections, in seconds.  */

  static unsigned int tcp_retry_limit = 15;

And used like:

  /* Check for timeout.  */
  if (*polls > tcp_retry_limit * POLL_INTERVAL)
    {
      errno = ETIMEDOUT;
      return -1;
    }

Which made me stop and look over why is it that 'polls' is signed.
What I found is there's really no reason.

gdb/
2013-03-26  Pedro Alves  <palves@redhat.com>

	* ser-tcp.c (wait_for_connect): Make 'polls' parameter unsigned.
	(net_open): Make 'polls' local unsigned.