[media] media: ov13858: Calculate pixel-rate at runtime, use mode

Calculate pixel-rate at run time instead of compile time.

Instead of using hardcoded pixels-per-line, extract it from current sensor
mode.

Signed-off-by: Chiranjeevi Rapolu <chiranjeevi.rapolu@intel.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>