[media] redrat3: remove memcpys and fix unaligned memory access

In stead of doing a memcpy from #defined offset, declare structs which
describe the incoming and outgoing data accurately.
Tested on first generation RedRat.

Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>