greybus: define more greybus classes

There are new protocols defined which don't belong to any existing
class, add more classes to support them.

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