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

Support RealView(R) Emulation Baseboard

modulename: realview_eb.ko

configname: CONFIG_MACH_REALVIEW_EB

Linux Kernel Configuration
└─>RealView platform type
└─>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.

source code: