ARM: dts: sun6i: Add SPDIF to the Mele I7

Enable the S/PDIF transmitter that is present on the Mele I7.

Signed-off-by: Marcus Cooper <codekipper@gmail.com>
Acked-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>