Display: Don't clear display callback listeners when starting a new exec.

Fixes https://github.com/RetroAchievements/RAIntegration/issues/1186

Core/HW/Display.cpp

@@ -308,7 +308,7 @@ int DisplayCalculateFrameSkip() {
 	return frameSkipNum;
 }
 
-void DisplayHWInit() {
+void DisplayHWReset() {
 	frameStartTicks = 0;
 	numVBlanks = 0;
 	isVblank = 0;
@@ -329,6 +329,8 @@ void DisplayHWInit() {
 	lastFrameTimeHistory = 0.0;
 }
 
+void DisplayHWInit() {}
+
 void DisplayHWShutdown() {
 	std::lock_guard<std::mutex> guard(listenersLock);
 	vblankListeners.clear();