CONFIG_440GX is not available for thedefaultarchitecture x86.
Result is shown for architecture ppc

CONFIG_440GX (not configurable)

modulename: ibm440gx.ko

and/or

ibm440gx_common.ko

configname: CONFIG_440GX

Linux Kernel Configuration
└─>IBM 4xx options
└─>440GX
In linux kernel since version 2.6.20 (release Date: 2007-02-04)  
source code:
arch/ppc/platforms/4xx/ibm440gx.c