CONFIG_MACH_U5500 is not available for the selected architecture x86.
Result is shown for architecture arm

U5500 Development platform

modulename: board-u5500.ko

configname: CONFIG_MACH_U5500

Ux500 target platform
└─>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/board-u5500.c

depends
 or CONFIG_ARCH_U8500 |
| CONFIG_UX500_SOC_DB5500