greybus: operation: Drop alignment attribute from operation message header

The buffers allocated for message header is already 64 bit aligned and
we have explicit pad bytes in the header structure, to 64 bit align the
operation specific data.

And so there is no need to add the aligned attribute to the operation
message header. Drop it.

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