Add a couple of tests on the XSCOM bus of the PowerNV machine for the
the POWER8 and POWER9 CPUs. The first tests reads the CFAM identifier
of the chip. The second test goes further in the XSCOM address space
and reaches the cores to read their DTS registers.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
[dwg: Fixed an incorrect indentation, and a Makefile problem]]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>