radeon_hd: Move out some DisplayPort common code

* General DisplayPort functions in common dp.cpp
* DP port information struct in common header
* Please don't use this private accelerant common DP
  code just yet as it is very early.

headers/private/graphics/common/dp.h

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2012 Haiku, Inc. All rights reserved.
+ * Distributed under the terms of the MIT License.
+ *
+ * Authors:
+ *      Alexander von Gluck, [email protected]
+ */
+#ifndef _DP_H
+#define _DP_H
+
+
+#include <Accelerant.h>
+#include "dp_raw.h"
+#include <GraphicsDefs.h>
+#include <OS.h>
+
+
+typedef struct {
+	// Required configuration
+	bool	valid;			// Is valid DP information
+	uint32	auxPin;			// Normally GPIO pin on GPU
+
+	uint8	config[8];		// DP Configuration Data
+	int		laneCount;
+
+	uint32	linkRate;		// DP Link Speed 162000, 270000, 540000
+
+	// Internal State information
+	uint8	linkStatus[DP_LINK_STATUS_SIZE];
+
+	bool    trainingUseEncoder;
+
+	uint8   trainingAttempts;
+	uint8   trainingSet[4];
+	int     trainingReadInterval;
+
+} dp_info;
+
+
+uint32 dp_encode_link_rate(uint32 linkRate);
+uint32 dp_decode_link_rate(uint32 rawLinkRate);
+
+uint32 dp_get_lane_count(dp_info* dpInfo, display_mode* mode);
+
+
+#endif /* _DP_H */