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/dsi/dsi_drm.c

@@ -771,6 +771,9 @@ int dsi_conn_set_info_blob(struct drm_connector *connector,
 		break;
 	}
 
+	sde_kms_info_add_keyint(info, "max os brightness", panel->bl_config.brightness_max_level);
+	sde_kms_info_add_keyint(info, "max panel backlight", panel->bl_config.bl_max_level);
+
 	if (panel->spr_info.enable)
 		sde_kms_info_add_keystr(info, "spr_pack_type",
 			msm_spr_pack_type_str[panel->spr_info.pack_type]);