CONFIG_MPC8xxx_GPIO is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

MPC8xxx GPIO support

modulename: mpc8xxx_gpio.ko

configname: CONFIG_MPC8xxx_GPIO

Linux Kernel Configuration
└─>Platform support
└─>MPC8xxx GPIO support
In linux kernel since version 2.6.28 (release Date: 2008-12-24)  
Say Y here if you're going to use hardware that connects to the
MPC831x/834x/837x/8572/8610 GPIOs.

source code:
arch/powerpc/sysdev/mpc8xxx_gpio.c