KVM: x86: trap AMD MSRs for the TSeg base and mask

commit 3afb1121800128aae9f5722e50097fcf1a9d4d88 upstream.

These have roughly the same purpose as the SMRR, which we do not need
to implement in KVM.  However, Linux accesses MSR_K8_TSEG_ADDR at
boot, which causes problems when running a Xen dom0 under KVM.
Just return 0, meaning that processor protection of SMRAM is not
in effect.

Reported-by: M A Young <m.a.young@durham.ac.uk>
Acked-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>