greybus: Prefix module-id with endo id

Prefix module-id with endo-id to uniquely identify it for the entire
kernel.

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