V4L/DVB (10443): cx18: Use correct line counts per field in firmware API call

The driver was incorrectly setting 0 line counts in a firmware
API call to set the maximum amount of lines per field.

Signed-off-by: Andy Walls <awalls@radix.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>