sunxi: Rename Astar_MID756 to Et_q8_v1_6 to match kernel dts name

Rename the Astar_MID756 to Et_q8_v1_6 to match the kernel dts name.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>