The tuner-types.h is part of the V4L2 core and should be
touched for every new tuner added. So, it deserves to be
documented at the device-drivers DocBook.

Add it to device-drivers.tmpl and add descriptions for
enum param_type and struct tuner_range.
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>