This is a pc & q35 only machine opt.

VMWare apparently doesn't like running under QEMU due to our
incomplete emulation of it's special IO Port.  This adds a
pc & q35 property to allow it to be turned off.
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NDon Slutz <dslutz@verizon.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>