drm/i915/tgl: Enable DDI/Port G

In TGL there we are missing the initialization of port G.
Do the same as for other ports.

Signed-off-by: Khaled Almahallawy <khaled.almahallawy@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191008220905.18278-1-khaled.almahallawy@intel.com