Include CDC ECM (Ethernet) function

configname: CONFIG_USB_FUNCTIONFS_ETH

USB Gadget Drivers
└─>Include CDC ECM (Ethernet) function
In linux kernel since version 2.6.35 (release Date: 2010-08-01)  
Include an CDC ECM (Ethernet) funcion in the CDC ECM (Funcion)
Filesystem. If you also say "y" to the RNDIS query below the
gadget will have two configurations.