zr364xx.rst: usb/devices is now at /sys/kernel/debug/

The /proc/bus/usb/devices got moved to sysfs. It is now
sitting at:
	/sys/kernel/debug/usb/devices

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>