tcp_westwood: use tcp_jiffies32 instead of tcp_time_stamp

This CC does not need 1 ms tcp_time_stamp and can use
the jiffy based 'timestamp'.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>