drm/sun4i: hdmi: Provide ddc symlink in sun4i hdmi connector sysfs directory

Use the ddc pointer provided by the generic connector.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/b5a8881b226a9af7d31eb6a57d7fe0fccdcb3a47.1564161140.git.andrzej.p@collabora.com