CONFIG_ATARI is not available for thedefaultarchitecture x86.
Result is shown for architecture m68k

Atari support

modulename: head.ko

configname: CONFIG_ATARI

Linux Kernel Configuration
└─>Atari support
In linux kernel since version 2.6.12  
This option enables support for the 68000-based Atari series of
computers (including the TT, Falcon and Medusa). If you plan to use
this kernel on an Atari, say Y here and browse the material
available in <file:Documentation/arch/m68k>; otherwise say N.

source code: