Some convinience fluff: Add support for '-vga virtio', also add
virtio-vga to the list of vga cards so '-device virtio-vga' will
turn off the default vga.
Written by Dave Airlie and Gerd Hoffmann.
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>