media: rc: fix race condition in ir_raw_event_store_edge() handling

There is a possible race condition between the IR timeout being generated
from the timer, and new IR arriving. This could result in the timeout
being added to the kfifo after new IR arrives. On top of that, there is
concurrent write access to the kfifo from ir_raw_event_store_edge() and
the timer.

Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>