net.c: Use proper socket type for __get_sock_name().

This patch gets rid of

	net.c:652:33: warning: incompatible pointer types passing 'int (int, __SOCKADDR_ARG, socklen_t *restrict)', expected 'int (*)(int, struct sockaddr *, socklen_t *)' [-pedantic]
	        return __get_sock_name(sockfd, getsockname);
	                                       ^~~~~~~~~~~

when compiling with clang.