spi/spi_s3c64xx: Increase dead reckoning time in wait_for_xfer()

For small transfers at high speeds the expected transfer time can easily
be well under 1ms, causing the delay in wait_for_xfer() to be only the
dead reckoning fudge factor of 5ms currently included. Experiments on
some of my systems shows that this is marginal for some transfers so
double it to 10ms.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Jassi Brar <jassi.brar@samsung.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

drivers/spi/spi_s3c64xx.c

@@ -320,7 +320,7 @@ static int wait_for_xfer(struct s3c64xx_spi_driver_data *sdd,
 
 	/* millisecs to xfer 'len' bytes @ 'cur_speed' */
 	ms = xfer->len * 8 * 1000 / sdd->cur_speed;
-	ms += 5; /* some tolerance */
+	ms += 10; /* some tolerance */
 
 	if (dma_mode) {
 		val = msecs_to_jiffies(ms) + 10;