drm/amd/display: add support for low bpc

[WHY&HOW]
Low bpc timings are failing validation, port a patch to allow them to pass.
Signed-off-by: Dillon Varone <dillon.varone@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dml/dcn32/display_mode_vba_util_32.c

@@ -1595,7 +1595,6 @@ double dml32_TruncToValidBPP(
 	unsigned int   NonDSCBPP0;
 	unsigned int   NonDSCBPP1;
 	unsigned int   NonDSCBPP2;
-	unsigned int   NonDSCBPP3;
 
 	if (Format == dm_420) {
 		NonDSCBPP0 = 12;
@@ -1604,10 +1603,9 @@ double dml32_TruncToValidBPP(
 		MinDSCBPP = 6;
 		MaxDSCBPP = 1.5 * DSCInputBitPerComponent - 1 / 16;
 	} else if (Format == dm_444) {
-		NonDSCBPP0 = 18;
-		NonDSCBPP1 = 24;
-		NonDSCBPP2 = 30;
-		NonDSCBPP3 = 36;
+		NonDSCBPP0 = 24;
+		NonDSCBPP1 = 30;
+		NonDSCBPP2 = 36;
 		MinDSCBPP = 8;
 		MaxDSCBPP = 3 * DSCInputBitPerComponent - 1.0 / 16;
 	} else {
@@ -1661,9 +1659,7 @@ double dml32_TruncToValidBPP(
 			else
 				return dml_floor(16.0 * MaxLinkBPP, 1.0) / 16.0;
 		} else {
-			if (MaxLinkBPP >= NonDSCBPP3)
-				return NonDSCBPP3;
-			else if (MaxLinkBPP >= NonDSCBPP2)
+			if (MaxLinkBPP >= NonDSCBPP2)
 				return NonDSCBPP2;
 			else if (MaxLinkBPP >= NonDSCBPP1)
 				return NonDSCBPP1;
@@ -1674,7 +1670,7 @@ double dml32_TruncToValidBPP(
 		}
 	} else {
 		if (!((DSCEnable == false && (DesiredBPP == NonDSCBPP2 || DesiredBPP == NonDSCBPP1 ||
-				DesiredBPP == NonDSCBPP0 || DesiredBPP == NonDSCBPP3)) ||
+				DesiredBPP <= NonDSCBPP0)) ||
 				(DSCEnable && DesiredBPP >= MinDSCBPP && DesiredBPP <= MaxDSCBPP)))
 			return BPP_INVALID;
 		else