drm/amd/display: Reduce dmesg error to a debug print

[Why & How]
Dmesg errors are found on dcn3.1 during reset test, but it's not
a really failure. So reduce it to a debug print.
Signed-off-by: Leo (Hanghong) Ma <hanghong.ma@amd.com>
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c

@@ -4454,7 +4454,7 @@ bool dp_retrieve_lttpr_cap(struct dc_link *link)
 				lttpr_dpcd_data,
 				sizeof(lttpr_dpcd_data));
 		if (status != DC_OK) {
-			dm_error("%s: Read LTTPR caps data failed.\n", __func__);
+			DC_LOG_DP2("%s: Read LTTPR caps data failed.\n", __func__);
 			return false;
 		}