CONFIG_MACH_MESON6 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Amlogic Meson6 (8726MX) SoCs support

configname: CONFIG_MACH_MESON6

Linux Kernel Configuration
└─>Amlogic Meson SoCs
└─>Amlogic Meson6 (8726MX) SoCs support
In linux kernel since version 3.18 (release Date: 2014-12-07)