spi/imx: remove redundant config.speed_hz setting

The config.speed_hz is just setted at the two lines ahead of it,
obviously we don't need to copy the code to set the config.speed_hz
again. Remove it for a cleanup.

Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: NSascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: NHui Wang <jason77.wang@gmail.com>
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>

drivers/spi/spi-imx.c

@@ -688,8 +688,6 @@ static int spi_imx_setupxfer(struct spi_device *spi,
 		config.speed_hz = spi->max_speed_hz;
 	if (!config.bpw)
 		config.bpw = spi->bits_per_word;
-	if (!config.speed_hz)
-		config.speed_hz = spi->max_speed_hz;
 
 	/* Initialize the functions for transfer */
 	if (config.bpw <= 8) {