[media] cx24120: Rework vco function to remove xxyyzz variable

Change calculate_vco function to send_vco to tidy up cx24120_init
function.
xxyyzz variable is remnants of a manual div & remainder codepath
to perform a u64 rounded div; replace with kernel macro
DIV_ROUND_CLOSEST_ULL
Hex values provided to the message are mainly variables calculated
within this function, replace with these to remove hardcoding.

Signed-off-by: Jemma Denson <jdenson@gmail.com>
Signed-off-by: Patrick Boettcher <patrick.boettcher@posteo.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>