CONFIG_ARCH_MV78XX0 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Marvell MV78xx0

configname: CONFIG_ARCH_MV78XX0

ARM system type
└─>Marvell MV78xx0
In linux kernel since version 2.6.27 (release Date: 2008-10-09)  
Support for the following Marvell MV78xx0 series SoCs:
MV781x0, MV782x0.