spi: update modalias_show after of_device_uevent_modalias support

Commit 3ce6c9e2 ("spi: add of_device_uevent_modalias support") is
incomplete, as it didn't update the modalias_show function to generate the
of: modalias string if available.

Fixes: 3ce6c9e2 ("spi: add of_device_uevent_modalias support")
Signed-off-by: Andreas Schwab <schwab@suse.de>
Link: https://lore.kernel.org/r/mvmwnpi4fya.fsf@suse.deSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi.c

@@ -58,6 +58,10 @@ modalias_show(struct device *dev, struct device_attribute *a, char *buf)
 	const struct spi_device	*spi = to_spi_device(dev);
 	int len;
 
+	len = of_device_modalias(dev, buf, PAGE_SIZE);
+	if (len != -ENODEV)
+		return len;
+
 	len = acpi_device_modalias(dev, buf, PAGE_SIZE - 1);
 	if (len != -ENODEV)
 		return len;