[media] rc: Remove ir-common module

Now, just one old bttv board uses the old RC5 raw decoding routines.
Its conversion to rc-core requires the generation of IRQ data for both
positive and negative transitions at the IRQ line. I'm not sure if
bttv driver supports it or if the transitions will be reliable enough.
So, due to the lack of hardware for testing, the better for now is to
just move the legacy routines to bttv driver, and wait for someone with
a Nebula Digi could help to port it to use also rc-core raw decoders.

Acked-by: Hermann Pitton <hermann-pitton@arcor.de>
Acked-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>