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

Support RealView(R) Emulation Baseboard


Linux Kernel Configuration
└─>ARM Ltd. RealView family
└─>Support RealView(R) Emulation Baseboard
In linux kernel since version 2.6.15 (release Date: 2006-01-02)  
Include support for the ARM(R) RealView(R) Emulation Baseboard
platform. On an ARMv5 kernel, this will include support for
the ARM926EJ-S core tile, while on an ARMv6/v7 kernel, at least
one of the ARM1136, ARM1176, ARM11MPCore or Cortex-A9MPCore
core tile options should be enabled.