minor: configurable default interface params before dhcp is up

[bruelltuete]

In cyw43_cb_tcpip_init(), there are some parameters configured for the interface before dhcp has had a chance to run. Would be nice if those were configurable (via macros?). Esp the google dns server probably warrants a more prominent entry in a config file, e.g. cyw43_configport.h. https://github.com/georgerobotics/cyw43-driver/blob/2ab6ca93f9cd044bc6f35c1403b1284e4161294a/src/cyw43_lwip.c#L143

[peterharperuk]

Yes, you're right.

[dpgeorge]

Fixed by 5f396836c8e9a748849b121377bf442388571716