Move local version put in tcp_diag.c into time.h
where it belongs.  Also, make it smarted about HZ
values math.

Based upon suggestions from Joe Perches <joe@Perches.com>
Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>