dt-bindings: dp-connector: describe separate DP and AUX lines

dt-bindings: dp-connector: describe separate DP and AUX lines

In some cases it's reasonable to describe DP lanes and AUX signal lines
separately in the DT. One of the typical reasons is if the source of DP
signals can support either USB-C or DP connections. In such a case the
transmitter of DP signals have separate ports: one for SS lanes and
another one for SBU / AUX signals.

Instead of leaving AUX signals from the controller unconnected, add an
option to the DT schema to AUX signal lines separately from the main
link lanes.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20250907-dp-conenctor-sbu-v1-1-de79c0fcd64d@oss.qualcomm.com
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>