greybus: add bundle class to the bundle uevent

When bundles are added and then removed, we have a race where we go to
read the sysfs file, but it is now for a different bundle than the
uevent was originally for.  So add the bundle class to the uevent so we
"know" what the correct bundle class was.

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