ARM: dts: sun8i: a33: Add the DSI-related nodes

The A33 has a MIPI-DSI block, along with its D-PHY. Let's add it in order
to use it in the relevant boards.

Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>