powerpc/pseries: Add hcall to read 4 ptes at a time in real mode

This adds plpar_pte_read_4_raw() which can be used read 4 PTEs from
PHYP at a time, while in real mode.

It also creates a new hcall9 which can be used in real mode.  It's the
same as plpar_hcall9 but minus the tracing hcall statistics which may
require variables outside the RMO.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>