net: wan: slic_ds26522: Export OF module alias information

When the device is registered via OF, the OF table is used to match the
driver instead of the SPI device ID table, but the entries in the later
are used as aliasses to load the module if the driver was not built-in.

This is because the SPI core always reports an SPI module alias instead
of an OF one, but that could change so it's better to always export it.

Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: David S. Miller <davem@davemloft.net>