sunxi: Add support for the CHIP Pro

The CHIP Pro is a SoM that features the GR8 SIP, an AXP209, a BT/WiFi chip
and a 512MiB SLC NAND.

This it's an SLC NAND, it doesn't suffer the same drawbacks than found on
the MLC NANDs, and we can enable it right away.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>