V4L/DVB: ir-core: Distinguish sysfs attributes for in-hardware and raw decoders

Some devices have in-hardware Remote Controller decoder, while others
need a software decoder to get the IR code. As each software decoder
can be enabled/disabled individually, allowing multiple protocol
decoding capability.

On the other hand, hardware decoders have a limited protocol
support, often being able of decoding just one protocol each time.
So, each type needs a different set of capabilities to control the
supported protocol(s).

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