To ease following guest accesses to the Bonito64 chipset,
map its I/O range as UnimplementedDevice.
We can now see the accesses to unimplemented peripheral
using the '-d unimp' command line option.

Reviewed-by: Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>
Message-id: <20200510210128.18343-9-f4bug@amsat.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>