CONFIG_SH_X3PROTO is not available for thedefaultarchitecture x86.
Result is shown for architecture sh

SH-X3 Prototype board

configname: CONFIG_SH_X3PROTO

Linux Kernel Configuration
└─>Board support
└─>SH-X3 Prototype board
In linux kernel since version 2.6.24 (release Date: 2008-01-24)  
selects
CONFIG_NO_IOPORT_MAP
CONFIG_IRQ_DOMAIN