greybus: connection: Send protocol version for firmware protocol

As per greybus specs, we need to send the protocol version for firmware
protocol and so this special case Hack.

Probably we should always send the protocol version AP supports and kill
this hack completely. But then it requires updates to specs as well, and
that should be done after some discussion.

For now, add a FIXME for that and a special case for firmware protocol.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>