Adding usb-ctrl from intel-bmc into phosphor-misc

[郁雷]

There is a script [usb-ctrl][1] hosted in intel-bmc.
It supports the VirtualMedia feature by insert/eject files to the host
as a USB mass-storage device.
Comparing to the existing [state_hook][2] in jsnbd, it supports
multiple UDCs, so it supports mount multiple files.

In addition, I have some updates on the usb-ctrl script to make it
support the USB ECM device, which creates a USB ethernet device
between BMC and the host.

So my proposal is to add the `usb-ctrl` script into the phosphor-misc
repo so that it gets reviewed and could be used by upstream.

Any ideas?

[1]: https://github.com/Intel-BMC/openbmc/blob/intel/meta-openbmc-mods/meta-common/recipes-core/fw-update/files/usb-ctrl
[2]: https://github.com/openbmc/openbmc/blob/master/meta-phosphor/aspeed-layer/recipes-connectivity/jsnbd/jsnbd/state_hook

-- 
BRs,
Lei YU