target/ppc: Correct RMLS table

target/ppc: Correct RMLS table

The table of RMA limits based on the LPCR[RMLS] field is slightly wrong.
We're missing the RMLS == 0 => 256 GiB RMA option, which is available on
POWER8, so add that.

The comment that goes with the table is much more wrong.  We *don't* filter
invalid RMLS values when writing the LPCR, and there's not really a
sensible way to do so.  Furthermore, while in theory the set of RMLS values
is implementation dependent, it seems in practice the same set has been
available since around POWER4+ up until POWER8, the last model which
supports RMLS at all.  So, correct that as well.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Greg Kurz <groug@kaod.org>