CONFIG_IRQ_CPU is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

CONFIG_IRQ_CPU (not configurable)

modulename: irq_cpu.ko

configname: CONFIG_IRQ_CPU

Linux/MIPS Kernel Configuration
└─>Machine selection
└─>IRQ_CPU
In linux kernel since version 2.6.12  
source code:
arch/mips/kernel/irq_cpu.c