powerpc: add PVR mask support

powerpc: add PVR mask support

IBM POWERPC processors encode PVR as a CPU family in higher 16 bits and
a CPU version in lower 16 bits. Since there is no significant change
in behavior between versions, there is no point to add every single CPU
version in QEMU's CPU list. Also, new CPU versions of already supported
CPU won't break the existing code.

This adds PVR value/mask support for KVM, i.e. for -cpu host option.

As CPU family class name for POWER7 is "POWER7-family", there is no need
to touch aliases.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Alexander Graf <agraf@suse.de>