ARM: dts: sunxi: Add missing dmas properties to TCON

The TCON binding mandates a dmas phandle to the DMAengine channel used for
that controller. However, since it's not used in the driver, some device
trees have been missing it. Let's add it.

Acked-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>