drm/i915/hdmi: Remove old i2c symlink

Remove the i915 specific i2c-N symlink from HDMI connectors.
This was added to sort of mirror the DP connectors that alreayd
had their aux ch based i2c adapter sitting beneath them in the
sysfs hierarchy. But now that we have the standard "ddc" symlink
approach provided by the core let's switch to that fully.
I don't think anything beyond igt depends on this.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230829113920.13713-12-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>