[media] v4l2: Add rangelow and rangehigh fields to the v4l2_hw_freq_seek struct

To allow apps to limit a hw-freq-seek to a specific band, for further
info see the documentation this patch adds for these new fields.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>