CONFIG_32BIT is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

32-bit kernel

modulename: ioremap.ko

and/or

module-elf32.ko

and/or

scall32-o32.ko

configname: CONFIG_32BIT

Kernel code model
└─>32-bit kernel
In linux kernel since version 2.6.14 (release Date: 2005-10-27)  
Select this option if you want to build a 32-bit kernel.

source code:
arch/mips/mm/


is selected by
CONFIG_SERIAL_DZ

is depended by
CONFIG_PMB