drm/amd/display: Set default bits per channel

[Why]
Bump into calcReducedBlankingTiming because of mode query failed.
In this function,
timing.displayColorDepth == DISPLAY_COLOR_DEPTH_UNDEFINED.
Then req_bw == 0 because of bits_per_channel == 0.
So decide edp link settings, use default RBRx1 for special timing.

[How]
Set default bits_per_channel is 8.
Signed-off-by: Jing Zhou <Jing.Zhou@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Eryk Brol <eryk.brol@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -3471,11 +3471,11 @@ uint32_t dc_bandwidth_in_kbps_from_timing(
 		bits_per_channel = 16;
 		break;
 	default:
+		ASSERT(bits_per_channel != 0);
+		bits_per_channel = 8;
 		break;
 	}
 
-	ASSERT(bits_per_channel != 0);
-
 	kbps = timing->pix_clk_100hz / 10;
 	kbps *= bits_per_channel;
 

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

@@ -1410,15 +1410,24 @@ static void print_status_message(
 	case LINK_RATE_LOW:
 		link_rate = "RBR";
 		break;
+	case LINK_RATE_RATE_2:
+		link_rate = "R2";
+		break;
+	case LINK_RATE_RATE_3:
+		link_rate = "R3";
+		break;
 	case LINK_RATE_HIGH:
 		link_rate = "HBR";
 		break;
-	case LINK_RATE_HIGH2:
-		link_rate = "HBR2";
-		break;
 	case LINK_RATE_RBR2:
 		link_rate = "RBR2";
 		break;
+	case LINK_RATE_RATE_6:
+		link_rate = "R6";
+		break;
+	case LINK_RATE_HIGH2:
+		link_rate = "HBR2";
+		break;
 	case LINK_RATE_HIGH3:
 		link_rate = "HBR3";
 		break;