Include 'pure' configuration

configname: CONFIG_USB_FUNCTIONFS_GENERIC

Linux Kernel Configuration
└─>Device Drivers
└─>USB support
└─>USB Gadget Support
└─>USB Gadget precomposed configurations
└─>Include 'pure' configuration
In linux kernel since version 2.6.35 (release Date: 2010-08-01)  
Include a configuration with the Function Filesystem alone with
no Ethernet interface.