esp32/network_lan: Make LAN.active(state) succeed if already in state.

This PR ensures that `network.LAN.active(True/False)` will succeed if the
LAN is already in the desired state.

Currently, `lan.active(True)` will raise an `OSError` exception if the LAN
is already in the desired state.  This is inconsistent with
`network.WLAN.active(True/False)` and causes `lan.active(True)` to raise an
exception after a soft reset (causing common network startup scripts to
fail for LAN interfaces).
Signed-off-by: Glenn Moloney <glenn.moloney@gmail.com>

ports/esp32/network_lan.c

@@ -312,13 +312,14 @@ static mp_obj_t lan_active(size_t n_args, const mp_obj_t *args) {
     lan_if_obj_t *self = MP_OBJ_TO_PTR(args[0]);
 
     if (n_args > 1) {
-        if (mp_obj_is_true(args[1])) {
+        bool make_active = mp_obj_is_true(args[1]);
+        if (make_active && !self->base.active) {
             esp_netif_set_hostname(self->base.netif, mod_network_hostname_data);
             self->base.active = (esp_eth_start(self->eth_handle) == ESP_OK);
             if (!self->base.active) {
                 mp_raise_msg(&mp_type_OSError, MP_ERROR_TEXT("ethernet enable failed"));
             }
-        } else {
+        } else if (!make_active && self->base.active) {
             self->base.active = !(esp_eth_stop(self->eth_handle) == ESP_OK);
             if (self->base.active) {
                 mp_raise_msg(&mp_type_OSError, MP_ERROR_TEXT("ethernet disable failed"));