drm/amd/display: Use DC log instead of using DM error msg

[Why & How]
It sent an error msg when it failed to read the DP tunneling DPCD field.
This should just be a warning msg. Use a DC log instead of a DM error msg.

Reviewed-by: Wenjing Liu <wenjing.liu@amd.com>
Signed-off-by: Cruise Hung <Cruise.Hung@amd.com>
Signed-off-by: Wayne Lin <wayne.lin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

Author: Cruise Hung

drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c

@@ -2023,7 +2023,7 @@ static bool retrieve_link_cap(struct dc_link *link)
 	/* Read DP tunneling information. */
 	status = dpcd_get_tunneling_device_data(link);
 	if (status != DC_OK)
-		dm_error("%s: Read DP tunneling device data failed.\n", __func__);
+		DC_LOG_DP2("%s: Read DP tunneling device data failed.\n", __func__);
 
 	retrieve_cable_id(link);
 	dpcd_write_cable_id_to_dprx(link);