CONFIG_PPC4xx_MSI is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

CONFIG_PPC4xx_MSI (not configurable)

modulename: ppc4xx_msi.ko

configname: CONFIG_PPC4xx_MSI

Linux Kernel Configuration
└─>PPC4xx_MSI
In linux kernel since version 3 (release Date: 2011-07-21)  
source code:
arch/powerpc/sysdev/ppc4xx_msi.c
depends
CONFIG_4xx
CONFIG_PCI
CONFIG_PCI_MSI