greybus: operation: fix outgoing-response corruption

Fix potential corruption of outgoing responses by verifying that the
operations is indeed outgoing when receiving a response.

Failure to do so could lead to an incoming response corrupting an
outgoing response that uses the same operation id.

Reported-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>