CONFIG_TOSHIBA_BOARDS is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

CONFIG_TOSHIBA_BOARDS (not configurable)

configname: CONFIG_TOSHIBA_BOARDS

Linux/MIPS Kernel Configuration
└─>TOSHIBA_BOARDS
In linux kernel since version 2.6.12  
is depended by
CONFIG_TOSHIBA_RBTX4927