drm/dp: add DPCD definitions from eDP 1.2

Mostly display control related DPCD addresses.
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Reviewed-by: NSonika Jindal <sonika.jindal@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

include/drm/drm_dp_helper.h

@@ -341,6 +341,38 @@
 
 #define DP_EDP_DPCD_REV			    0x700    /* eDP 1.2 */
 
+#define DP_EDP_GENERAL_CAP_1		    0x701
+
+#define DP_EDP_BACKLIGHT_ADJUSTMENT_CAP     0x702
+
+#define DP_EDP_GENERAL_CAP_2		    0x703
+
+#define DP_EDP_DISPLAY_CONTROL_REGISTER     0x720
+
+#define DP_EDP_BACKLIGHT_MODE_SET_REGISTER  0x721
+
+#define DP_EDP_BACKLIGHT_BRIGHTNESS_MSB     0x722
+#define DP_EDP_BACKLIGHT_BRIGHTNESS_LSB     0x723
+
+#define DP_EDP_PWMGEN_BIT_COUNT             0x724
+#define DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN     0x725
+#define DP_EDP_PWMGEN_BIT_COUNT_CAP_MAX     0x726
+
+#define DP_EDP_BACKLIGHT_CONTROL_STATUS     0x727
+
+#define DP_EDP_BACKLIGHT_FREQ_SET           0x728
+
+#define DP_EDP_BACKLIGHT_FREQ_CAP_MIN_MSB   0x72a
+#define DP_EDP_BACKLIGHT_FREQ_CAP_MIN_MID   0x72b
+#define DP_EDP_BACKLIGHT_FREQ_CAP_MIN_LSB   0x72c
+
+#define DP_EDP_BACKLIGHT_FREQ_CAP_MAX_MSB   0x72d
+#define DP_EDP_BACKLIGHT_FREQ_CAP_MAX_MID   0x72e
+#define DP_EDP_BACKLIGHT_FREQ_CAP_MAX_LSB   0x72f
+
+#define DP_EDP_DBC_MINIMUM_BRIGHTNESS_SET   0x732
+#define DP_EDP_DBC_MAXIMUM_BRIGHTNESS_SET   0x733
+
 #define DP_SIDEBAND_MSG_DOWN_REQ_BASE	    0x1000   /* 1.2 MST */
 #define DP_SIDEBAND_MSG_UP_REP_BASE	    0x1200   /* 1.2 MST */
 #define DP_SIDEBAND_MSG_DOWN_REP_BASE	    0x1400   /* 1.2 MST */