[media] cx24120: minor checkpatch fixes

This patch fixes printk-related checkpatch warnings. All printks
have been converted to pr_warn or pr_info or pr_err.

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