esp_eth_driver_uninstall() function

- ESP_OK: uninstall esp_eth driver successfully - ESP_ERR_INVALID_ARG: uninstall esp_eth driver failed because of some invalid argument - ESP_ERR_INVALID_STATE: uninstall esp_eth driver failed because it has more than one reference - ESP_FAIL: uninstall esp_eth driver failed because some other error occurred

It's not recommended to uninstall Ethernet driver unless it won't get used any more in application code. To uninstall Ethernet driver, you have to make sure, all references to the driver are released. Ethernet driver can only be uninstalled successfully when reference counter equals to one.