Add printout of some SoC error status registers, and dump the SLB contents
for those machine check events where it makes sense.

Since we can't go about and ioremap registers at machine check time,
and we generally want to do as little as possible to print out the
information, pre-build a table of the registers to dump and their address
in the common PCI config space range.
Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>