CONFIG_ARCH_KEYSTONE is not available for thedefaultarchitecture x86.
Result is shown for architecture arm
Texas Instruments Keystone Devices
configname: CONFIG_ARCH_KEYSTONE
Linux Kernel Configuration
└─>Texas Instruments Keystone Devices
In linux kernel since version 3.10 (release Date: 2013-06-30)
Support for boards based on the Texas Instruments Keystone family of
SoCs.
SoCs.