init: usb: Add init scripts for configfs commands

This CL adds a new init script init.usb.configfs.rc
to add generic configfs commands. Setting
sys.usb.configfs in init.usb.{hardware}.rc
enables executing commands in this script

Bug=23633457

Change-Id: Iaae844a7957d6c9bf510648aaff86d56aa0c6243