V4L/DVB: IR/imon: set up mce-only devices w/mce keytable

Currently, they get set up with the pad keytable, which they can't
actually use at all. Also add another variant of volume scancodes from
another 0xffdc device, and properly set up the 0x9e 0xffdc device as an
iMON VFD w/MCE proto IR.

Based on data and a prior patch from Anders Eriksson on the lirc list.

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