CONFIG_UX500_AUTO_PLATFORM is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

CONFIG_UX500_AUTO_PLATFORM (not configurable)

configname: CONFIG_UX500_AUTO_PLATFORM

Linux Kernel Configuration
└─>ST-Ericsson U8500 Series
└─>UX500_AUTO_PLATFORM
In linux kernel since version 3.1 (release Date: 2011-10-24)  
At least one platform needs to be selected in order to build
a working kernel. If everything else is disabled, this
automatically enables MACH_MOP500.