drivers: esp_at: fix net_if_get_by_iface() typo

s/net_if_get_by_ifindex/net_if_get_by_iface/

Fixes: 0e57844 ("drivers: wifi: esp_at: Bind DNS to device net
  interface")
Signed-off-by: Marcin Niestroj <m.niestroj@emb.dev>

Author: mniestroj

drivers/wifi/esp_at/esp.c

@@ -494,7 +494,7 @@ static void esp_dns_work(struct k_work *work)
 	size_t i;
 	int err, ifindex;
 
-	ifindex = net_if_get_by_ifindex(data->net_iface);
+	ifindex = net_if_get_by_iface(data->net_iface);
 
 	for (i = 0; i < ESP_MAX_DNS; i++) {
 		if (!addrs[i].sin_addr.s_addr) {