[media] rc-core: add support for IR raw transmitters

IR raw transmitter driver type is specified in the enum
rc_driver_type as RC_DRIVER_IR_RAW_TX which includes all those
devices that transmit raw stream of bit to a receiver.

The data are provided by userspace applications, therefore they
don't need any input device allocation, but still they need to be
registered as raw devices.

Suggested-by: Sean Young <sean@mess.org>
Signed-off-by: Andi Shyti <andi.shyti@samsung.com>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>