CONFIG_LOONGSON_MACH3X is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

Generic Loongson 3 family machines

modulename: fixup-loongson3.ko

configname: CONFIG_LOONGSON_MACH3X

Machine Type
└─>Generic Loongson 3 family machines
In linux kernel since version 3.10 (release Date: 2013-06-30)  
Generic Loongson 3 family machines utilize the 3A/3B revision
of Loongson processor and RS780/SBX00 chipset.

source code:
arch/mips/pci/