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

Marvell Kirkwood

configname: CONFIG_ARCH_KIRKWOOD

ARM system type
└─>Marvell Kirkwood
In linux kernel since version 2.6.27 (release Date: 2008-10-09)  
Support for the following Marvell Kirkwood series SoCs:
88F6180, 88F6192 and 88F6281.