drm/i915/tc: fix the reset of ln0

Setting ln0 similar to ln1

Fixes: 3b51be4e ("drm/i915/tc: Update DP_MODE programming")
Cc: <stable@vger.kernel.org> # v5.5+
Signed-off-by: Khaled Almahallawy <khaled.almahallawy@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200608204537.28468-1-khaled.almahallawy@intel.com