CONFIG_MACH_OX820 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Support OX820 Based Products

configname: CONFIG_MACH_OX820

Linux Kernel Configuration
└─>Oxford Semiconductor OXNAS Family SoCs
└─>Support OX820 Based Products
In linux kernel since version 4.1 (release Date: 2015-06-21)  
Include Support for the Oxford Semiconductor OX820 SoC Based Products.