drm/connector: Set DDC pointer in drmm_connector_init

Commit 35a3b82f ("drm/connector: Introduce drmm_connector_init")
introduced the function drmm_connector_init() with a parameter for an
optional ddc pointer to the i2c controller used to access the DDC bus.

However, the underlying call to __drm_connector_init() was always
setting it to NULL instead of passing the ddc argument around.

This resulted in unexpected null pointer dereference on platforms
expecting to get a DDC controller.

Fixes: 35a3b82f ("drm/connector: Introduce drmm_connector_init")
Signed-off-by: Maxime Ripard <maxime@cerno.tech>