drm/dp: DPCD register defines for link status within ESI field

Link status is available in the ESI field on devices with DPCD r1.2 or
higher. DP spec also says "An MST upstream device shall use this field
instead of the Link/Sink Device Status field registers, starting from DPCD
Address 00200h."

v2: Prefixed DP_ (Jani)
    Rewrote commment to stay within 80 cols.
Cc: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170914062127.12047-1-dhinakaran.pandiyan@intel.com

include/drm/drm_dp_helper.h

@@ -738,6 +738,11 @@
 #define DP_RECEIVER_ALPM_STATUS		    0x200b  /* eDP 1.4 */
 # define DP_ALPM_LOCK_TIMEOUT_ERROR	    (1 << 0)
 
+#define DP_LANE0_1_STATUS_ESI                  0x200c /* status same as 0x202 */
+#define DP_LANE2_3_STATUS_ESI                  0x200d /* status same as 0x203 */
+#define DP_LANE_ALIGN_STATUS_UPDATED_ESI       0x200e /* status same as 0x204 */
+#define DP_SINK_STATUS_ESI                     0x200f /* status same as 0x205 */
+
 #define DP_DPRX_FEATURE_ENUMERATION_LIST    0x2210  /* DP 1.3 */
 # define DP_GTC_CAP					(1 << 0)  /* DP 1.3 */
 # define DP_SST_SPLIT_SDP_CAP				(1 << 1)  /* DP 1.4 */