drm/i915/tc: Clear DKL_TX_PMD_LANE_SUS before program voltage swing

This sequence was recently added to fix internal HW sequences to
reset TC ports.

HSDES: 1507287614
HSDES: 14010071447
BSpec: 49292
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191021223408.87344-1-jose.souza@intel.com