CONFIG_ARCH_STI is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

STMicroelectronics Consumer Electronics SOCs

modulename: board-dt.ko

configname: CONFIG_ARCH_STI

Linux Kernel Configuration
└─>STMicroelectronics Consumer Electronics SOCs
In linux kernel since version 3.10 (release Date: 2013-06-30)  
Include support for STiH41x SOCs like STiH415/416 using the device tree
for discovery
More information at Documentation/arm/STiH41x and
at
source code:
arch/arm/mach-sti/board-dt.c