spapr: Enable ISA 3.0 MMU mode selection via CAS

spapr: Enable ISA 3.0 MMU mode selection via CAS

Add the new node, /chosen/ibm,arch-vec-5-platform-support to the
device tree. This allows the guest to determine which modes are
supported by the hypervisor.

Update the option vector processing in h_client_architecture_support()
to handle the new MMU bits. This allows guests to request hash or
radix mode and QEMU to create the guest's HPT at this time if it is
necessary but hasn't yet been done.  QEMU will terminate the guest if
it requests an unavailable mode, as required by the architecture.

Extend the ibm,pa-features node with the new ISA 3.0 values
and set the radix bit if KVM supports radix mode. This probably won't
be used directly by guests to determine the availability of radix mode
(that is indicated by the new node added above) but the architecture
requires that it be set when the hardware supports it.

If QEMU is using KVM, and KVM is capable of running in radix mode,
guests can be run in real-mode without allocating a HPT (because KVM
will use a minimal RPT). So in this case, we avoid creating the HPT
at reset time and later (during CAS) create it if it is necessary.

ISA 3.0 guests will now begin to call h_register_process_table(),
which has been added previously.

Signed-off-by: Sam Bobroff <sam.bobroff@au1.ibm.com>
[dwg: Strip some unneeded prefix from error messages]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>