V4L/DVB (9762): em28xx: fix tuner absent entries

Before this patch, several devices without tuner were kept the value 0
for tuner_type. However, this means TUNER_TEMIC_PAL. Replace those
entries for the proper TUNER_ABSENT value.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>