[media] rc/mceusb: timeout should be in ns, not us

Fixes an egregious bug in mceusb driver, where the receiver was being
put into idle mode far sooner than it should have, thanks to storing a
timeout value that in us where it should be ns. Basically, the receiver
kept going into idle mode before a trailing space had been fully
received, which was causing problems for some protocols, most notably
manifesting as lirc userspace never receiving a trailing space for any
rc5 signals.

Signed-off-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>