pseries: Add real mode debugging hcalls

pseries: Add real mode debugging hcalls

PAPR systems support several hypercalls intended for use in real mode
debugging tools.  These implement reads and writes to arbitrary guest
physical addresses.  This is useful for real mode software because it
allows access to IO addresses and memory outside the RMA without going
through the somewhat involved process of setting up the hash page table
and enabling translation.

We want these so that when we add real IO devices, the SLOF firmware can
boot from them without having to enter virtual mode.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: David Gibson <dwg@au1.ibm.com>
Signed-off-by: Alexander Graf <agraf@suse.de>