If the kernel is built without e.g. the imon IR decoder, the protocols
sysfs file still show the protocol as available. If user-space tries to
enable this decoder, the kernel will report an error:

$ echo +imon > /sys/class/rc/rc0/protocols
[   57.693033] rc_core: Loaded IR protocol module ir-imon-decoder, but protocol imon still not available

Ensuring that unavailable protocols are not advertised, ensures that
users space knows it is not available, and a BPF based IR decoder can be
loaded instead.

This supports the case when no kernel-based codec needs to be compiled in,
and every IR decoder can be BPF based.

Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>