drm/sun4i: hdmi: Add A31 specific DDC register definitions

The DDC block for the HDMI controller is different on the A31.

This patch adds the register definitions.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171010032008.682-9-wens@csie.org