netutils/netinit: Perform icmpv6 autoconfiguration when link transitions from down to up.

Without this addition, icmpv6 is never configured in the case that the
device is powered on without an ethernet cable connected.

netutils/netinit/netinit.c

@@ -873,6 +873,11 @@ static int netinit_monitor(void)
                   goto errout_with_notification;
                 }
 
+#ifdef CONFIG_NET_ICMPv6_AUTOCONF
+              /* Perform ICMPv6 auto-configuration */
+
+              netlib_icmpv6_autoconfiguration(ifr.ifr_name);
+#endif
               /* And wait for a short delay.  We will want to recheck the
                * link status again soon.
                */