pkg/lwip: Set netdev callback before driver init
pkg/lwip: Set netdev callback before driver init

Otherwise if the cable is connected at boot the immediate NETDEV_EVENT_ISR
event signaling connection will not trigger the isr, and the netdev will not
clear its pending event.

This explains why the connect/rx event clash seen in "esp32/eth: Don't
overwrite queued event with RX packet" (95196fb7e40b12c7) only happened
with lwIP.

Now on my ESP32 board with Ethernet the issue was the opposite (since IDF
upgrade), the stuck connected event blocked receive from working. After
this change 95196fb7e40b12c7 can be reverted since even early events are
consumed properly.

kaspar030/RIOT,ant9000/RIOT,kYc0o/RIOT,ant9000/RIOT,kaspar030/RIOT,kaspar030/RIOT,miri64/RIOT,kYc0o/RIOT,ant9000/RIOT,miri64/RIOT,kYc0o/RIOT,jasonatran/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,miri64/RIOT,kaspar030/RIOT,jasonatran/RIOT,jasonatran/RIOT,RIOT-OS/RIOT,RIOT-OS/RIOT,miri64/RIOT,kYc0o/RIOT,RIOT-OS/RIOT,miri64/RIOT,RIOT-OS/RIOT,jasonatran/RIOT,ant9000/RIOT,jasonatran/RIOT,kYc0o/RIOT,ant9000/RIOT