Make setting chunk_size and buffer_size mandatory for drivers which
expect lirc_dev to allocate the lirc_buffer (i.e. ir-lirc-codec) and
don't set them in lirc-zilog (which creates its own buffer).

Also remove an unnecessary copy of chunk_size in struct irctl (the
same information is already available from struct lirc_buffer).
Signed-off-by: David Härdeman <david@hardeman.nu>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>