greybus: ap: fix svc handshake protocol check

Fix incorrect SVC handshake protocol check, which would only bail out if
both major and minor protocol versions supported by the SVC differed.

Since we currently only support one version of the protocol, upgrade the
debug message to warning and bail unless the protocol versions match
perfectly for now.

Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>