drm/i915/adlp: Add TypeC PHY TBT->DP-alt/legacy mode switch workaround

Add display workaround # 1309179469 , which fixes a PHY hang when
switching from TBT mode to DP-alt/legacy mode. The workaround also
requires an IFWI/PHY firmware change, before that this change has no
effect (the DKL_PCS_DW5/SOFTRESET flag is always cleared).

HSDES: 18018237866
HSDES: 16014473319

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220218122611.767974-1-imre.deak@intel.com