vmsvga: fix vmsvga_update_display

Fix standard vga mode check:  Both s->config and s->enabled must be set
to enable vmware command fifo processing.

Drop dirty tracking code from the fifo rendering code path, it isn't
used anyway because vmsvga turns off dirty tracking when leaving
standard vga mode.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-id: 20170421091632.30900-9-kraxel@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
