[media] rc: use time unit conversion macros correctly

Due to my own stupidity, some of the wrong time unit conversion macros
were being used inside some of the IR drivers I've been working on. Fix
that, and convert over some additional places to also use the macros.

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