KVM: x86: AMD Processor Topology Information

This patch allow to enable x86 feature TOPOEXT. This is needed to provide
information about SMT on AMD Zen CPUs to the guest.

Signed-off-by: Stanislav Lanci <pixo@polepetko.eu>
Tested-by: Nick Sarnie <commendsarnex@gmail.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Babu Moger <babu.moger@amd.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>