Documentation: ABI: sysfs-class-udc: remove duplicated entry

maximum_speed entry was duplicated. Remove one instance.

Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

usb: gadget: udc: add a 'function' sysfs file

This file will print out the name of the currently running USB Gadget
Driver. It can be read even when there are no functions loaded.

Suggested-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

usb: gadget: udc: document our sysfs ABI

I noticed that this has been missing for quite
some time so I decided it was about time to
document it.

Signed-off-by: Felipe Balbi <balbi@ti.com>