spi: Clean up probe and remove functions

While backporting 33cf00e ("spi: attach/detach SPI device to the ACPI
power domain"), I noticed that the code changes were suboptimal:

* Why use &spi->dev when we have dev at hand?

* After fixing the above, spi is used only once, so we don't really
  need a local variable for it.

This results in the following clean-up.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Mark Brown <broonie@linaro.org>

drivers/spi/spi.c

@@ -255,25 +255,23 @@ EXPORT_SYMBOL_GPL(spi_bus_type);
 static int spi_drv_probe(struct device *dev)
 {
 	const struct spi_driver		*sdrv = to_spi_driver(dev->driver);
-	struct spi_device		*spi = to_spi_device(dev);
 	int ret;
 
-	acpi_dev_pm_attach(&spi->dev, true);
-	ret = sdrv->probe(spi);
+	acpi_dev_pm_attach(dev, true);
+	ret = sdrv->probe(to_spi_device(dev));
 	if (ret)
-		acpi_dev_pm_detach(&spi->dev, true);
+		acpi_dev_pm_detach(dev, true);
 
 	return ret;
 }
 
 static int spi_drv_remove(struct device *dev)
 {
 	const struct spi_driver		*sdrv = to_spi_driver(dev->driver);
-	struct spi_device		*spi = to_spi_device(dev);
 	int ret;
 
-	ret = sdrv->remove(spi);
-	acpi_dev_pm_detach(&spi->dev, true);
+	ret = sdrv->remove(to_spi_device(dev));
+	acpi_dev_pm_detach(dev, true);
 
 	return ret;
 }