CONFIG_HAVE_SMP is not available for the default architecture x86.
Result is shown for architecture xtensa

System Supports SMP (MX)

configname: CONFIG_HAVE_SMP

Linux Kernel Configuration
└─> Processor type and features
└─> System Supports SMP (MX)

This option is use to indicate that the system-on-a-chip (SOC)
supports Multiprocessing. Multiprocessor support implemented above
the CPU core definition and currently needs to be selected manually.

Multiprocessor support in implemented with external cache and
interrupt controllers.

The MX interrupt distributer adds Interprocessor Interrupts
and causes the IRQ numbers to be increased by 4 for devices
like the open cores ethernet driver and the serial interface.

You still have to select "Enable SMP" to enable SMP on this SOC.