[media] smiapp: Gather information on valid link rate and BPP combinations

Not all link rates are possible with all BPP values.

Also rearrange other initialisation a little. Obtaining possible PLL
configurations earlier requires that.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>