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

CONFIG_PLAT_ORION (not configurable)

configname: CONFIG_PLAT_ORION

Linux Kernel Configuration
└─>System Type
└─>PLAT_ORION
In linux kernel since version 2.6.26 (release Date: 2008-07-13)  
is selected by
CONFIG_MV643XX_ETH

is depended by
CONFIG_ARCH_ORION5X