[media] rc: fix buffer overrun

"[media] rc-core: move timeout and checks to lirc" introduced a buffer
overrun by passing the number of bytes, rather than the number of samples,
to the transmit function.

Signed-off-by: Sean Young <sean@mess.org>
Acked-by: David Härdeman <david@hardeman.nu>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>