CONFIG_AMIGA is not available for the default architecture x86.
Result is shown for architecture m68k

Amiga support

modulename: head.ko
configname: CONFIG_AMIGA

Linux Kernel Configuration
└─> Amiga support

In linux kernel since version 2.6.12  

This option enables support for the Amiga series of computers. If
you plan to use this kernel on an Amiga, say Y here and browse the
material available in <file:Documentation/arch/m68k>; otherwise say N.

source code: