mmc: mmc_spi: Export OF module alias information

Drivers needs to export the OF id table and this be built into
the module or udev won't have the necessary information to autoload
the driver module when the device is registered via OF.

Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>