greybus: Documentation/sysfs: rename the svc eject attribute

The svc eject attribute was added as an interim solution and is still
used to implement a form of forced ejection.

This will soon be superseded by the module eject attribute, which will
provide an interface for clean eject. We may keep the forced-eject
mechanism around indefinitely, albeit possibly with a different name
(e.g. forced_intf_eject). Either way, update the example tree to reflect
the actual name, intf_eject, which currently used for this svc attribute.

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