when configure a invalid vram size for cirrus card, such as less
2 MB, which will crash qemu. Follow the real hardware, the cirrus
card has 4 MB video memory. Also for backward compatibility, accept
8 MB and 16 MB vram size.
Signed-off-by: NGonglei <arei.gonglei@huawei.com>
Reviewed-by: NAndreas Färber <afaerber@suse.de>
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>