[media] IR: make sure we register the input device when it is safe to do so

As soon as input device is registered, it might be accessed (and it is)
This can trigger a hardware interrupt that can access
not yet initialized ir->raw, (by sending a sample)

This can be reproduced by holding down a remote button and reloading the module.
And this always crashes the systems where hardware decides to send an interrupt
right at the moment it is enabled.

Signed-off-by: Maxim Levitsky <maximlevitsky@gmail.com>
Acked-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>