ppc: Remove stub support for 32-bit hypervisor mode

ppc: Remove stub support for 32-bit hypervisor mode

a4f30719a8cd, way back in 2007 noted that "PowerPC hypervisor mode is not
fundamentally available only for PowerPC 64" and added a 32-bit version
of the MSR[HV] bit.

But nothing was ever really done with that; there is no meaningful support
for 32-bit hypervisor mode 13 years later.  Let's stop pretending and just
remove the stubs.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Fabiano Rosas <farosas@linux.ibm.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>