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

CONFIG_ARM_ASM_UNIFIED (not configurable)

configname: CONFIG_ARM_ASM_UNIFIED

Linux Kernel Configuration
└─>Kernel Features
└─>ARM_ASM_UNIFIED
In linux kernel since version 2.6.32 (release Date: 2009-12-02)  
is depended by
CONFIG_THUMB2_KERNEL