drm/vmwgfx: Enable traces *after* we've hidden SVGA

Hiding SVGA seems to trigger a VGA screen clear, and with no
traces dirty it doesn't seem to repaint

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Dmitry Torokhov <dtor@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>