[media] rc: allow software timeout to be set

Both the iguanair and the technotrend usb ir do not do any timeout
handling in hardware, so timeout is entirely done in
ir_raw_event_store_with_filter(). Any sensible timeout value will
do, so allow it to be set using LIRC_SET_REC_TIMEOUT.

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