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

CONFIG_MIPS_FIXUP_BIGPHYS_ADDR (not configurable)

configname: CONFIG_MIPS_FIXUP_BIGPHYS_ADDR

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