can: mcp251x: Allow tuning SPI mode and limit maximal SPI speed

Patch allow to use different mode settings for SPI (MODE3 for example)
and limit maximal speed according to IC datasheet.
Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/mcp251x.c

@@ -1082,7 +1082,11 @@ static int mcp251x_can_probe(struct spi_device *spi)
 	SET_NETDEV_DEV(net, &spi->dev);
 
 	/* Configure the SPI bus */
-	spi->mode = SPI_MODE_0;
+	spi->mode = spi->mode ? : SPI_MODE_0;
+	if (mcp251x_is_2510(spi))
+		spi->max_speed_hz = spi->max_speed_hz ? : 5 * 1000 * 1000;
+	else
+		spi->max_speed_hz = spi->max_speed_hz ? : 10 * 1000 * 1000;
 	spi->bits_per_word = 8;
 	spi_setup(spi);