sunxi: video: Fallback from HDMI to VGA on boards with VGA

If a board has no LCD, but does have VGA fallback to VGA when no HDMI cable
is connected (unless hpd=0).

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
sunxi: video: Add VGA output support

Add support for VGA directly from the sunxi SoC / display engine.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>