disp: msm: sde: add support for digital dimming

Add a new connector property to allow DC dimming feature to set
dimming backlight LUT. This change also adds a connector event
for client to register for backlight info needed for digital dimming
feature, including OS brightness, OS brightness_max, panel_backlight,
panel_backlight_max, and scale factors from ABA and LTM features.

Change-Id: I78f713fb2b965ca24effd973b4dfa9ff07a852f8
Signed-off-by: Ping Li <pingli@codeaurora.org>

msm/msm_drv.h

@@ -198,6 +198,7 @@ enum msm_mdp_conn_property {
 	CONNECTOR_PROP_PP_CWB_DITHER,
 	CONNECTOR_PROP_HDR_METADATA,
 	CONNECTOR_PROP_DEMURA_PANEL_ID,
+	CONNECTOR_PROP_DIMMING_BL_LUT,
 
 	/* # of blob properties */
 	CONNECTOR_PROP_BLOBCOUNT,