net/ethernet: fix compilation issues for inet_sockif.c

[HedongGao]

Summary

When the CONFIG_NET_SOCKOPTS, CONFIG_NET_TIMESTAMP, and CONFIG_NET_UDP_NO_STACK configuration options are enabled and the CONFIG_NET_UDP configuration option is disabled, a compilation error is generated. Modifications have been made to address the aforementioned issues.

inet/inet_sockif.c:772:40: error: invalid use of undefined type ‘struct udp_conn_s’ 772 | *(FAR int *)value = (conn->timestamp != 0); | ^~ inet/inet_sockif.c: In function ‘inet_set_socketlevel_option’: inet/inet_sockif.c:1081:19: error: invalid use of undefined type ‘struct udp_conn_s’ 1081 | conn->timestamp = (*((FAR int *)value) != 0);

Impact

No modifications have been made to the functionality, so it will not affect the system.

Testing

As mentioned above, with the above configuration, modifying the code and recompiling, the problem will no longer recur.