sunxi: Add support for android boot image

When using the fastboot boot command, the image sent to U-Boot will be an
Android boot image. If the support is missing, that obviously won't work,
so we need it in our configuration.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>