spi/mpc52xx: Fix device remove function

The call sequence spi_alloc_master/spi_register_master/spi_unregister_master is
complete; it reduces the device reference count to zero, which results in
device memory being freed. An extra call to spi_master_put is unnecessary
and results in an access to free memory.

At the same time, since the call to spi_unregister_master results in device
memory being freed, it must no longer be accessed afterwards.

To fix both problems, call spi_master_get to get an extra reference to the
device, and call spi_master_put only after the last access to device data.
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/spi/spi-mpc52xx.c

@@ -529,7 +529,7 @@ static int __devinit mpc52xx_spi_probe(struct platform_device *op)
 
 static int __devexit mpc52xx_spi_remove(struct platform_device *op)
 {
-	struct spi_master *master = dev_get_drvdata(&op->dev);
+	struct spi_master *master = spi_master_get(dev_get_drvdata(&op->dev));
 	struct mpc52xx_spi *ms = spi_master_get_devdata(master);
 	int i;
 
@@ -541,8 +541,8 @@ static int __devexit mpc52xx_spi_remove(struct platform_device *op)
 
 	kfree(ms->gpio_cs);
 	spi_unregister_master(master);
-	spi_master_put(master);
 	iounmap(ms->regs);
+	spi_master_put(master);
 
 	return 0;
 }