boards: native_sim: Detect attempt to configure not existing int

Similar to e770128c. Prevent overrunning the irq vector table.
This is not happening today in tree, but coverity thinks it
does. Checking for it to prevent it is not a bad idea
anyhow, so let's do it.

Signed-off-by: Krzysztof Chruściński <krzysztof.chruscinski@nordicsemi.no>