[media] ir-core: convert drivers/media/video/cx88 to ir-core

This patch converts the cx88 driver (for sampling hw) to use the
decoders provided by ir-core instead of the separate ones provided
by ir-functions (and gets rid of those).

The value for MO_DDS_IO had a comment saying it corresponded to
a 4kHz samplerate. That comment was unfortunately misleading. The
actual samplerate was something like 3250Hz.

The current value has been derived by analyzing the elapsed time
between interrupts for different values (knowing that each interrupt
corresponds to 32 samples).

Thanks to Mariusz Bialonczyk <manio@skyboo.net> for testing my patches
(about one a day for two weeks!) on actual hardware.

Signed-off-by: David Härdeman <david@hardeman.nu>
Acked-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>