spi_mpc83xx: fix clockrate calculation for low speed

Commit a61f5345 (spi_mpc83xx clockrate fixes) broke clockrate calculation
for low speeds.  SPMODE_DIV16 should be set if the divider is higher than
64, not only if the divider gets clipped to 1024.

Furthermore, the clipping check was off by a factor 16 as well.
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/spi/spi_mpc83xx.c

@@ -267,17 +267,14 @@ int mpc83xx_spi_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
 	cs->hw_mode |= SPMODE_LEN(bits_per_word);
 
 	if ((mpc83xx_spi->spibrg / hz) > 64) {
-		pm = mpc83xx_spi->spibrg / (hz * 64);
-		if (pm > 16) {
 		cs->hw_mode |= SPMODE_DIV16;
-			pm /= 16;
+		pm = mpc83xx_spi->spibrg / (hz * 64);
 		if (pm > 16) {
 			dev_err(&spi->dev, "Requested speed is too "
 				"low: %d Hz. Will use %d Hz instead.\n",
 				hz, mpc83xx_spi->spibrg / 1024);
 			pm = 16;
 		}
-		}
 	} else
 		pm = mpc83xx_spi->spibrg / (hz * 4);
 	if (pm)