spi: acpi: Initialize modalias from of_compatible

When using devicetree spi_device.modalias is set to the compatible
string with the vendor prefix removed. For SPI devices described via
ACPI the spi_device.modalias string is initialized by acpi_device_hid.
When using ACPI and DT ids this string ends up something like "PRP0001".

Change acpi_register_spi_device to use the of_compatible property if
present. This makes it easier to instantiate spi drivers through ACPI
with DT ids.
Signed-off-by: Dan O'Donovan <dan@emutex.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Tested-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Acked-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/spi/spi.c

@@ -1722,13 +1722,15 @@ static acpi_status acpi_register_spi_device(struct spi_master *master,
 		return AE_OK;
 	}
 
+	acpi_set_modalias(adev, acpi_device_hid(adev), spi->modalias,
+			  sizeof(spi->modalias));
+
 	if (spi->irq < 0)
 		spi->irq = acpi_dev_gpio_irq_get(adev, 0);
 
 	acpi_device_set_enumerated(adev);
 
 	adev->power.flags.ignore_parent = true;
-	strlcpy(spi->modalias, acpi_device_hid(adev), sizeof(spi->modalias));
 	if (spi_add_device(spi)) {
 		adev->power.flags.ignore_parent = false;
 		dev_err(&master->dev, "failed to add SPI device %s from ACPI\n",