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

U8500 Snowball platform

configname: CONFIG_MACH_SNOWBALL

Linux Kernel Configuration
└─>ST-Ericsson U8500 Series
└─>U8500 Snowball platform
In linux kernel since version 3.1 (release Date: 2011-10-24)  
Include support for the snowball development platform.