drm: don't link DP aux i2c adapter to the hardware device node

drm: don't link DP aux i2c adapter to the hardware device node

The i2c adapter on DP AUX is purely a software construct. Linking
it to the device node of the parent device is wrong, as it leads to
2 devices sharing the same device node, which is bad practice, as
well as the i2c trying to populate children of the i2c adapter by
looking at the child device nodes of the parent device.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170113173630.22138-1-l.stach@pengutronix.de