The tuner ops g_frequency, g_tuner and s_tuner require that the tuner type
field is filled in. Document this.
The tuner-core doc is based on a patch from Mauro Carvalho Chehab <[email protected]>.
Signed-off-by: Hans Verkuil <[email protected]>
Signed-off-by: Mauro Carvalho Chehab <[email protected]>