Assert BSP_INTERRUPT_VECTOR_MAX + 1 == BSP_INTERRUPT_VECTOR_COUNT.
After building all BSPs with this patch, BSP_INTERRUPT_VECTOR_MAX can be
removed and replaced by BSP_INTERRUPT_VECTOR_COUNT. The
BSP_INTERRUPT_VECTOR_COUNT allows a default implementation which supports no
interrupt vector at all. Using COUNT instead of MAX may avoid some
interpretation issues, for example is the maximum value a valid vector number
or not.
Update #3269.
Remove BSP_INTERRUPT_VECTOR_MIN and unconditionally let interrupt vector
numbers start with zero.
The BSP_INTERRUPT_VECTOR_MIN == 0 invariant was tested by the previous commit
and building all BSPs.
Update #3269.
