media: smiapp: Turn limit lookup into a function

Instead of direct array access, turn accessing limit information into a
function. Going forward, more elaborate CCS limits will replace most SMIA
limits, and conversion will be less complicated this way.
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>