esp-netif: ppp netif to use netif_is_link_up() to update interface state
esp-netif: ppp netif to use netif_is_link_up() to update interface state

Closes https://github.com/espressif/esp-idf/issues/5069

espressif/esp-idf,espressif/esp-idf,espressif/esp-idf,espressif/esp-idf