V4L/DVB: cx22702: Some things never change

The init sequence never changes so it can be marked const. Likewise,
cx22702_ops is a template and can thus be made read-only.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>