spi: fix resource leak for drivers without .remove callback

Consider an spi driver with a .probe but without a .remove callback (e.g.
rtc-ds1347). The function spi_drv_probe() is called to bind a device and
so dev_pm_domain_attach() is called. As there is no remove callback
spi_drv_remove() isn't called at unbind time however and so calling
dev_pm_domain_detach() is missed and the pm domain keeps active.

To fix this always use both spi_drv_probe() and spi_drv_remove() and
make them handle the respective callback not being set. This has the
side effect that for a (hypothetical) driver that has neither .probe nor
remove the clk and pm domain setup is done.

Fixes: 33cf00e5 ("spi: attach/detach SPI device to the ACPI power domain")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20201119161604.2633521-1-u.kleine-koenig@pengutronix.deSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi.c

@@ -405,9 +405,11 @@ static int spi_drv_probe(struct device *dev)
 	if (ret)
 		return ret;
 
-	ret = sdrv->probe(spi);
-	if (ret)
-		dev_pm_domain_detach(dev, true);
+	if (sdrv->probe) {
+		ret = sdrv->probe(spi);
+		if (ret)
+			dev_pm_domain_detach(dev, true);
+	}
 
 	return ret;
 }
@@ -415,9 +417,10 @@ static int spi_drv_probe(struct device *dev)
 static int spi_drv_remove(struct device *dev)
 {
 	const struct spi_driver		*sdrv = to_spi_driver(dev->driver);
-	int ret;
+	int ret = 0;
 
-	ret = sdrv->remove(to_spi_device(dev));
+	if (sdrv->remove)
+		ret = sdrv->remove(to_spi_device(dev));
 	dev_pm_domain_detach(dev, true);
 
 	return ret;
@@ -442,10 +445,8 @@ int __spi_register_driver(struct module *owner, struct spi_driver *sdrv)
 {
 	sdrv->driver.owner = owner;
 	sdrv->driver.bus = &spi_bus_type;
-	if (sdrv->probe)
-		sdrv->driver.probe = spi_drv_probe;
-	if (sdrv->remove)
-		sdrv->driver.remove = spi_drv_remove;
+	sdrv->driver.probe = spi_drv_probe;
+	sdrv->driver.remove = spi_drv_remove;
 	if (sdrv->shutdown)
 		sdrv->driver.shutdown = spi_drv_shutdown;
 	return driver_register(&sdrv->driver);