[media] tea575x-tuner: mark VIDIOC_S_HW_FREQ_SEEK as an invalid ioctl

The tea575x-tuner framework can support the VIDIOC_S_HW_FREQ_SEEK for only
some of the tea575x-based boards. Mark this ioctl as invalid if the board
doesn't support it.

This fixes an issue with S_HW_FREQ_SEEK in combination with priority handling:
since the priority check is done first it could return -EBUSY, even though
calling the S_HW_FREQ_SEEK ioctl would return -ENOTTY. It should always return
ENOTTY in such a case.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>