drm/i915/tgl: Return the mg/dkl pll as DDI clock for new TC ports

TGL added 2 more TC ports that currently are not being handled by
icl_pll_to_ddi_clk_sel(), so adding those.

Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Reported-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190924210040.142075-6-jose.souza@intel.com