check timeout even if userspace

[edvardxyz]

After this commit we wait for tx window space or connection timeout.
If we lose connection we will get stuck indefinitely, waiting for tx window.

libcsp/src/csp_rdp.c

Lines 803 to 820 in cb3f265

	int csp_rdp_send(csp_conn_t * conn, csp_packet_t * packet) {
	if (conn->rdp.state != RDP_OPEN) {
	csp_rdp_error("RDP %p: ERROR cannot send, connection not open (%d)\n", (void *)conn, conn->rdp.state);
	return CSP_ERR_RESET;
	}
	/* Wait here for RDP to become ready or the connection to be closed */
	while (1) {
	if (conn->rdp.state == RDP_CLOSE_WAIT || conn->rdp.state == RDP_CLOSED) {
	csp_rdp_error("RDP %p: ERROR cannot send, connection closed by peer or timeout\n", (void *)conn);
	return CSP_ERR_RESET;
	}
	if (csp_rdp_is_conn_ready_for_tx(conn) == true)
	break;
	csp_rdp_protocol("RDP %p: Waiting for window update before sending seq %u\n", (void *)conn, conn->rdp.snd_nxt);
	csp_bin_sem_wait(&conn->rdp.tx_wait, conn->rdp.conn_timeout);
	}

Because we block the userspace with csp_send they can't use

libcsp/src/csp_rdp.c

Line 946 in cb3f265

bool csp_rdp_conn_is_active(csp_conn_t *conn) {

I assume we do not want to do the connection check inside csp_rdp_send?