display: Add hook for triggering screen update

DSI command mode panels do not need to be refreshed on each
vsync. Due to one frame latency in CABL LUT calculation, when CABL is
enabled for DSI command mode panels, the LUT doesnt get updated for last
frame. Triggering an extra update for DSI command mode panels fixes it.

Change-Id: I7a22e338609430746dda4d3081ff199109a95035
diff --git a/libqservice/QService.cpp b/libqservice/QService.cpp
index 8fc7319..54e285c 100644
--- a/libqservice/QService.cpp
+++ b/libqservice/QService.cpp
@@ -63,6 +63,14 @@
     mClient = client;
 }
 
+android::status_t QService::screenRefresh() {
+    status_t result = NO_ERROR;
+    if(mClient.get()) {
+        result = mClient->notifyCallback(SCREEN_REFRESH, 0);
+    }
+    return result;
+}
+
 void QService::init()
 {
     if(!sQService) {