V4L/DVB: IR/lirc: add docbook info covering lirc device interface

First ever crack at creating docbook documentation... Contains a bevy of
information on the various lirc device interface ioctls, as well as a
bit about the read and write interfaces.

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