[media] cx24120: Remove unneccesary assignments in cx24120_init

Probably a remnant of this driver being reverse engineered,
cx24120_init assigned ret on each call to writereg - they're not
used for anything so remove them to clear up the codebase.

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>