libusrsctp.recipe: Disable inet/inet6 code

We don't need this at all, since we use SCTP for WebRTC data channels and we'll never need the library to write to a socket. All the SCTP data is wrapped inside a DTLS packet and sent using something else (like libnice).

This code was cargo-culted from the Ericsson OpenWebRTC cerbero fork, but we've never needed it.