CONFIG_MACH_SPEAR600 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm
CONFIG_MACH_SPEAR600 (not configurable)
configname: CONFIG_MACH_SPEAR600
Linux Kernel Configuration
└─>MACH_SPEAR600
In linux kernel since version 2.6.35 (release Date: 2010-08-01)
Supports ST SPEAr600 boards configured via the device-tree