drm/i915/hdcp: Use correct aux for capability check scenario

Send the correct aux rather than the one derived
from intel_digital_port so that the HDCP version of both monitors
are fetched rather than just the primary one's

Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230830073437.666263-3-suraj.kandpal@intel.com