Revert "amdgpu/dc: drop dml_util_is_420"

This reverts commit e5bcf3d8.

Unfortunately these clash with our DML update from the HW guys.
Will attempt to reroll them after.
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dml/dml_common_defs.c

@@ -59,3 +59,36 @@ unsigned int dml_round_to_multiple(
 	else
 		return (num - remainder);
 }
+
+bool dml_util_is_420(enum source_format_class sorce_format)
+{
+	bool val = false;
+
+	switch (sorce_format) {
+	case dm_444_16:
+		val = false;
+		break;
+	case dm_444_32:
+		val = false;
+		break;
+	case dm_444_64:
+		val = false;
+		break;
+	case dm_420_8:
+		val = true;
+		break;
+	case dm_420_10:
+		val = true;
+		break;
+	case dm_422_8:
+		val = false;
+		break;
+	case dm_422_10:
+		val = false;
+		break;
+	default:
+		BREAK_TO_DEBUGGER();
+	}
+
+	return val;
+}

drivers/gpu/drm/amd/display/dc/dml/dml_common_defs.h

@@ -32,6 +32,7 @@
 
 #define DTRACE(str, ...) dm_logger_write(mode_lib->logger, LOG_DML, str, ##__VA_ARGS__);
 
+bool dml_util_is_420(enum source_format_class sorce_format);
 double dml_round(double a);
 unsigned int dml_round_to_multiple(
 			unsigned int num, unsigned int multiple, bool up);