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

Supplement the appended DTB with traditional ATAG information


Linux Kernel Configuration
└─>Boot options
└─>Supplement the appended DTB with traditional ATAG information
In linux kernel since version 3.1 (release Date: 2011-10-24)  
Some old bootloaders can't be updated to a DTB capable one, yet
they provide ATAGs with memory configuration, the ramdisk address,
the kernel cmdline string, etc. Such information is dynamically
provided by the bootloader and can't always be stored in a static
DTB. To allow a device tree enabled kernel to be used with such
bootloaders, this option allows zImage to extract the information
from the ATAG list and store it at run time into the appended DTB.