Fifo: Fix SyncGPU.

CBoot::BootUp() did call CoreTiming::Advance which itself blocks on the GPU,
but the GPU thread wasn't started already. This commit moves the SyncGPU
initialization into the Fifo.cpp file and call it after BootUp().

Source/Core/Core/CoreTiming.cpp

@@ -446,7 +446,7 @@ void Idle()
 		//the VI will be desynchronized. So, We are waiting until the FIFO finish and
 		//while we process only the events required by the FIFO.
 		ProcessFifoWaitEvents();
-		Fifo::Update(0);
+		Fifo::FlushGpu();
 	}
 
 	idledCycles += DowncountToCycles(PowerPC::ppcState.downcount);