chdrv_wait_for_lock wrongly assume chbsp_timestamp_ms() is available

Hi All,

in chirp driver ch_driver.c the fucntion chdrv_wait_for_lock() :

int chdrv_wait_for_lock(ch_dev_t *dev_ptr, uint16_t timeout_ms) {

	uint32_t start_time = chbsp_timestamp_ms();

	int ch_err = !(dev_ptr->sensor_connected);
	while (!ch_err && !(dev_ptr->get_locked_state(dev_ptr))) {

		chbsp_delay_ms(10);

		ch_err = ((chbsp_timestamp_ms() - start_time) > timeout_ms);

	}
#ifdef CHDRV_DEBUG

	if (ch_err) {

		char cbuf[80];

		snprintf(cbuf, sizeof(cbuf), "Sensor %hhu initialization timed out or missing\n", dev_ptr->io_index);

		chbsp_print_str(cbuf);

	}

#endif
	return ch_err;

}

the function use chbsp_timestamp_ms() however this call is marked as RECOMMENDED instead of REQUIRED, so it's not necessary available.
I proposed to use alternative way for timeout purpose ex:

        uint8_t locked = 0;

        uint32_t cnt = 0;

	while (cnt <= timeout_ms) {

		locked = dev_ptr->get_locked_state(dev_ptr);

		// DBG_OUT("get_locked_state:%d\n", locked);

		if (locked > 0 ) {

			break;

		}

		chbsp_delay_ms(10);

		cnt += 10;
	}

to avoid chbsp_timestamp_ms() call.