CONFIG_SYS_HAS_CPU_LOONGSON64 is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

CONFIG_SYS_HAS_CPU_LOONGSON64 (not configurable)

configname: CONFIG_SYS_HAS_CPU_LOONGSON64

Linux Kernel Configuration
└─>CPU selection
└─>SYS_HAS_CPU_LOONGSON64
In linux kernel since version 5.1 (release Date: 2019-05-05)