[media] rc: Set rdev before irq setup

This fixes a problem in fintek-cir and nuvoton-cir where the
irq handler would trigger during module load before the rdev member was
set, causing a NULL pointer crash.
It seems this crash is very reproducible (just bombard the receiver with
IR signals during module load), probably because when request_irq is
called, any pending intterupt is handled immediately, before
request_irq returns and rdev can be set.
This same crash was supposed to be fixed by commit
9ef449c6 ("[media] rc: Postpone ISR
registration"), but the crash was still observed on the nuvoton-cir
driver.
This commit was tested on nuvoton-cir only.

Cc: Jarod Wilson <jarod@redhat.com>
Signed-off-by: Matthijs Kooijman <matthijs@stdin.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>