CONFIG_40x is not available for thedefaultarchitecture x86.
Result is shown for architecture ppc

40x

modulename: 4xx_mmu.ko

and/or

xilinx_pic.ko

and/or

ppc403_pic.ko

and/or

ppc4xx_pic.ko

and/or

ppc4xx_setup.ko

configname: CONFIG_40x

Processor Type
└─>40x
In linux kernel since version 2.6.15 (release Date: 2006-01-02)  
source code:
arch/ppc/mm/4xx_mmu.c