Not all bits in SMRAM and ESMRAMC can be changed by the guest.
Add wmask defines accordingly and set them in mch_reset().
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>