spi: Limit the spi device max speed to controller's max speed

Make sure the max_speed_hz of spi_device does not override
the max_speed_hz of controller.
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20201209173514.93328-1-tudor.ambarus@microchip.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi.c

@@ -3369,7 +3369,8 @@ int spi_setup(struct spi_device *spi)
 	if (status)
 		return status;
 
-	if (!spi->max_speed_hz)
+	if (!spi->max_speed_hz ||
+	    spi->max_speed_hz > spi->controller->max_speed_hz)
 		spi->max_speed_hz = spi->controller->max_speed_hz;
 
 	mutex_lock(&spi->controller->io_mutex);