[media] doc-rst: update CEC_RECEIVE

The timestamp field was split into rx_ts and tx_ts, and the rx/tx_status
fields were moved. Update the doc accordingly.

Also fix a bug that stated that a non-zero tx_status field signaled an
error. That's not true, since TX_STATUS_OK is 1, not 0.

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