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

Physical address of main memory

configname: CONFIG_PHYS_OFFSET

Linux Kernel Configuration
└─>Physical address of main memory
In linux kernel since version 2.6.19 (release Date: 2006-11-29)  
Please provide the physical address corresponding to the
location of main memory in your system.