ARM: sun7i: dt: enable audio codec on Cubietruck

This commit enables the on-chip audio codec present on the A20 SoC
for the Cubietruck.

Signed-off-by: Emilio López <emilio@elopez.com.ar>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Chen-Yu Tsai <wens@csie.org>