CONFIG_CPU_MIPSR2_IRQ_EI is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

External interrupt controller mode

configname: CONFIG_CPU_MIPSR2_IRQ_EI

Linux/MIPS Kernel Configuration
└─>Kernel type
└─>MIPSR2 Interrupt handling
└─>External interrupt controller mode
In linux kernel since version 2.6.15 (release Date: 2006-01-02)  
Extended interrupt mode takes advantage of an external interrupt
controller to allow fast dispatching from many possible interrupt
sources. Say N unless you know that external interrupt support is
required.