media: smiapp: Support probing NVM size

The interface supports probing for the NVM size but this was not
implemented in the driver. Do that now.

This will also make nokia,nvm-size property redundant.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>