drm/imx: ldb: drop custom DDC bus support

drm/imx: ldb: drop custom DDC bus support

None of the boards ever supported by the upstream kernel used the custom
DDC bus support with the LDB connector. If a need arises to do so, one
should use panel-simple and its DDC bus code. Drop ddc-i2c-bus support
from the imx-ldb driver.

Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Tested-by: Chris Healy <cphealy@gmail.com>
Tested-by: Philipp Zabel <p.zabel@pengutronix.de> # on imx6q-nitrogen6x
Link: https://patchwork.freedesktop.org/patch/msgid/20240602-drm-imx-cleanup-v3-6-e549e2a43100@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>