greybus: send operation result in response message header

greybus: send operation result in response message header

Define a result byte in an operation response message header.

All the protocols now define the mandatory status as the first
byte in their response message.  Assume that, for the moment,
and save that value into the header result field (until we can
get the simulator set up to handle the new protocol).

Record the result from the response header as the result of the
overall operation.

Start enforcing the rule that we ignore all response payload (in
fact, the entire message) if we see a non-zero result value.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>