fix DHCP sleep time to msecond.

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@190 bbd45198-f89e-11dd-88c7-29a3b14d5316

net/lwip/src/arch/sys_arch_init.c

@@ -44,7 +44,7 @@ void lwip_sys_init()
 
     while (netif_default->ip_addr.addr == 0)
 	{
-        rt_thread_delay(DHCP_FINE_TIMER_MSECS);
+        rt_thread_delay(DHCP_FINE_TIMER_MSECS * RT_TICK_PER_SECOND / 1000);
 
         dhcp_fine_tmr();
         mscnt += DHCP_FINE_TIMER_MSECS;