CONFIG_ARCH_ORION5X is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Marvell Orion

configname: CONFIG_ARCH_ORION5X

ARM system type
└─>Marvell Orion
In linux kernel since version 2.6.26 (release Date: 2008-07-13)  
Support for the following Marvell Orion 5x series SoCs:
Orion-1 (5181), Orion-VoIP (5181L), Orion-NAS (5182),
Orion-2 (5281), Orion-1-90 (6183).