[media] cx25840: fix probing of cx2583x chips

Fix the probing of cx2583x chips, because two controls were clustered
that are not created for these chips.

This regression was introduced in 2.6.36.

Signed-off-by: Sven Barth <pascaldragon@googlemail.com>
Signed-off-by: Andy Walls <awalls@md.metrocast.net>
Cc: stable@kernel.org
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>