CONFIG_64BIT_PHYS_ADDR is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

CONFIG_64BIT_PHYS_ADDR (not configurable)

configname: CONFIG_64BIT_PHYS_ADDR

Linux/MIPS Kernel Configuration
└─>Kernel type
└─>64BIT_PHYS_ADDR
In linux kernel since version 2.6.12  
is depended by
CONFIG_NLM_XLP_BOARD