CONFIG_PPC4xx_GPIO is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

PPC4xx GPIO support

modulename: ppc4xx_gpio.ko

configname: CONFIG_PPC4xx_GPIO

Linux Kernel Configuration
└─>PPC4xx GPIO support
In linux kernel since version 2.6.28 (release Date: 2008-12-24)  
Enable gpiolib support for ppc40x based boards

source code:
arch/powerpc/sysdev/ppc4xx_gpio.c

depends
CONFIG_40x