CONFIG_TOSHIBA_RBTX4927 is not available for the selected architecture x86.
Result is shown for architecture mips

Toshiba RBTX49[23]7 board

modulename: fixup-rbtx4927.ko

configname: CONFIG_TOSHIBA_RBTX4927

Linux Kernel Configuration
└─>Toshiba RBTX49[23]7 board
In linux kernel since version 2.6.12 )
This Toshiba board is based on the TX4927 processor. Say Y here to
support this machine type
source code:
arch/mips/pci/fixup-rbtx4927.c