Fix memory corruption if >2 ports

src/core/iomgr/tcp_server_posix.c

@@ -252,7 +252,7 @@ static int add_socket_to_server(grpc_tcp_server *s, int fd,
     if (s->nports == s->port_capacity) {
       s->port_capacity *= 2;
       s->ports =
-          gpr_realloc(s->ports, sizeof(server_port *) * s->port_capacity);
+          gpr_realloc(s->ports, sizeof(server_port) * s->port_capacity);
     }
     sp = &s->ports[s->nports++];
     sp->server = s;