[media] cec: add cec_transmit_attempt_done helper function

A simpler variant of cec_transmit_done to be used where the HW does
just a single attempt at a transmit. So if the status indicates an
error, then the corresponding error count will always be 1 and this
function figures that out based on the status argument.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>