arm: quick hack to allow a greater number of CPUs to a guest OS

arm: quick hack to allow a greater number of CPUs to a guest OS

This is a quick hack to communicate a greater number of CPUs to a guest OS via
the ARM A9 SCU config register. Some OSes (Linux) just look at the bottom field
to count CPUs and with a small change can look at bits [3:0] to learn about up
to 16 CPUs.

Very much unsupported (and contains warning messages as such) but useful for
running 8 core sims without hardwiring CPU count in the guest OS.