spi: ath79: Fix module autoload for OF registration

If the driver is built as a module, autoload won't work because the module
alias information is not filled. So user-space can't match the registered
device with the corresponding module.

Export the module alias information using the MODULE_DEVICE_TABLE() macro.

Before this patch:

$ modinfo drivers/spi/spi-ath79.ko | grep alias
alias: platform:ath79-spi

After this patch:

$ modinfo drivers/spi/spi-ath79.ko | grep alias
alias: platform:ath79-spi
alias: of:N*T*Cqca,ar7100-spiC*
alias: of:N*T*Cqca,ar7100-spi

Signed-off-by: Javier Martinez Canillas <[e-mail]>
Signed-off-by: Mark Brown <[e-mail]>

drivers/spi/spi-ath79.c

···
 	{ .compatible = "qca,ar7100-spi", },
 	{ },
 };
+MODULE_DEVICE_TABLE(of, ath79_spi_of_match);
 
 static struct platform_driver ath79_spi_driver = {
 	.probe		= ath79_spi_probe,