V4L/DVB (10989): cx25840: cx23885 detection was broken

An earlier commit accidentally broke the detection of the cx25837 part of
the cx23885. Reinstated the commented out code.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>