greybus: Documentation: Arrange entries in alphabetical order

The order of entries in sysfs-bus-greybus file doesn't match the order
files/directories in sysfs on a real board. More specifically, N-svc
comes at last and ap_interface_id comes before endo_id within the svc.

Fix that.

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