[media] et8ek8: Export OF device ID as module aliases

The I2C core always reports a MODALIAS of the form i2c:<foo> even if the
device was registered via OF, this means that exporting the OF device ID
table device aliases in the module is not needed. But in order to change
how the core reports modaliases to user-space, it's better to export it.

Before this patch:

$ modinfo drivers/media/i2c/et8ek8/et8ek8.ko | grep alias
alias:          i2c:et8ek8

After this patch:

$ modinfo drivers/media/i2c/et8ek8/et8ek8.ko | grep alias
alias:          i2c:et8ek8
alias:          of:N*T*Ctoshiba,et8ek8C*
alias:          of:N*T*Ctoshiba,et8ek8

Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>