drm/i915/hdcp: Send the correct aux for DPMST HDCP scenario

Up until now we were sending the base aux stored in dig_port which
is not correct as this causes an issue when monitor is connected via
a DPMST hub causing it to be remote hence we end up seeing AUX
failures so let's send the remote aux in case of DPMST.

Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Arun R Murthy <arun.r.mruthy@intel.com>
Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230828063401.600414-4-suraj.kandpal@intel.com