CONFIG_PHYSICAL_START_BOOL is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

Set physical address where the kernel is loaded

configname: CONFIG_PHYSICAL_START_BOOL

Linux Kernel Configuration
└─>Advanced setup
└─>Set physical address where the kernel is loaded
In linux kernel since version 2.6.26 (release Date: 2008-07-13)  
This gives the physical address where the kernel is loaded.

Say N here unless you know what you are doing.