ppc: Add real mode CI load/store instructions for P7 and P8

Those instructions are only available in hypervisor real mode and
allow cache inhibited garded access to devices in that mode.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
[clg: fixed checkpatch.pl errors ]
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>