CONFIG_MACH_U5500 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

U5500 Development platform

modulename: board-u5500.ko

configname: CONFIG_MACH_U5500

Linux Kernel Configuration
└─>Ux500 target platform (boards)
└─>U5500 Development platform
In linux kernel since version 2.6.35 (release Date: 2010-08-01)  
Include support for the U5500 development platform.

source code:
/arch/arm/mach-ux500/