drm/i915/tgl: Add vbt value mapping for DDC Bus pin

Add VBT-value to DDC bus pin mapping for the same.

Signed-off-by: Mahesh Kumar <mahesh1.kumar@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190711173115.28296-20-lucas.demarchi@intel.com