media: ov13858: Correct link-frequency and pixel-rate

Previously both link-frequency and pixel-rate reported by
the sensor was incorrect, resulting in incorrect FPS.
Report link-frequency in Hz rather than link data rate in bps.
Calculate pixel-rate from link-frequency.

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@s-opensource.com>