CONFIG_ARCH_EXYNOS is not available for thedefaultarchitecture x86.
Result is shown for architecture arm64

ARMv8 based Samsung Exynos SoC family

modulename: exynos.ko

configname: CONFIG_ARCH_EXYNOS

Linux Kernel Configuration
└─>Platform selection
└─>ARMv8 based Samsung Exynos SoC family
In linux kernel since version 3.1 (release Date: 2011-10-24)  
This enables support for ARMv8 based Samsung Exynos SoC family.