DSPCore: Make g_cycles_left a regular member variable of DSPEmitter

Gets rid of a global within the DSP core.

Source/Core/Core/State.cpp

@@ -71,7 +71,7 @@ static Common::Event g_compressAndDumpStateSyncEvent;
 static std::thread g_save_thread;
 
 // Don't forget to increase this after doing changes on the savestate system
-static const u32 STATE_VERSION = 74;  // Last changed in PR 4408
+static const u32 STATE_VERSION = 75;  // Last changed in PR 4857
 
 // Maps savestate versions to Dolphin versions.
 // Versions after 42 don't need to be added to this list,