[media] lirc_parallel: build on smp and kill dead code

Talked to Christoph Bartelmus about this a bit, and he says this driver
actually *should* work okay on CONFIG_SMP, the check was a legacy one
from the very early days of SMP support before it had stabilized (yes,
this driver is that ancient).

Also remove some completely unused code, only noticed after building
this driver for the first time in an eternity (on an SMP host now, of
course).

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