[media] smiapp-pll: Calculate OP clocks only for sensors that have them

Profile 0 sensors have no OP clock branck in the clock tree. The PLL
calculator still calculated them, they just weren't used for anything.

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>