[media] lirc: validate transmission ir data

The lirc interface allows 255 u32 spaces and pulses, which are usec. If
the driver can handle this (e.g. winbond-cir) you can produce hours of
meaningless IR data and there is no method of interrupting it.

Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>