drivers: wifi: siwx91x: Fix SLAAC other configuration issues

The interface was properly set "dormant" on disconnect. However on startup,
it arrived in the system with "awake" status. Hence, some configuration
frames were sent before the interface was connected. Then, when the
interface was marked awake after the connection, the frames were not sent
again since the operational mode did not changed.

Therefore, Router Solicitations were not send, the Router Advertisements
were not received and the IPv6 address was not set.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>

Author: jerome-pouiller

drivers/wifi/siwx91x/siwx91x_wifi.c

@@ -1489,6 +1489,9 @@ static void siwx91x_iface_init(struct net_if *iface)
 	}
 	net_if_set_link_addr(iface, sidev->macaddr.octet, sizeof(sidev->macaddr.octet),
 			     NET_LINK_ETHERNET);
+	if (IS_ENABLED(CONFIG_WIFI_SILABS_SIWX91X_NET_STACK_NATIVE)) {
+		net_if_dormant_on(sidev->iface);
+	}
 	siwx91x_sock_init(iface);
 	siwx91x_ethernet_init(iface);