CONFIG_CPU_V7M_NUM_IRQ is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Number of external interrupts connected to the NVIC

configname: CONFIG_CPU_V7M_NUM_IRQ

Linux Kernel Configuration
└─>Number of external interrupts connected to the NVIC
In linux kernel since version 4.1 (release Date: 2015-06-21)  
This option indicates the number of interrupts connected to the NVIC.
The value can be larger than the real number of interrupts supported
by the system, but must not be lower.
The default value is 240, corresponding to the maximum number of
interrupts supported by the NVIC on Cortex-M family.

If unsure, keep default value.

depends
CONFIG_CPU_V7M