greybus: firmware: Add new status types for backend updated request

The specification got updated with two more status values, add their
support in greybus.

As retry isn't really an error, skip printing error messages for it as
well.

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