CONFIG_ETRAX_USB_HOST is not available for thedefaultarchitecture x86.
Result is shown for architecture cris

USB host

configname: CONFIG_ETRAX_USB_HOST

Linux Kernel Configuration
└─>USB host
In linux kernel since version 2.6.12  
This option enables the host functionality of the ETRAX 100LX
built-in USB controller. In host mode the controller is designed
for CTRL and BULK traffic only, INTR traffic may work as well
however (depending on the requirements of timeliness).