audio_core: pass in memory reference

Because HLE::Source is initialized as an array in the member initializer, it is hard to let it accept the reference on ctor, so it has a second init stage performed by DspHle::Impl::Impl

src/audio_core/hle/source.h

@@ -14,6 +14,10 @@
 #include "audio_core/interpolate.h"
 #include "common/common_types.h"
 
+namespace Memory {
+class MemorySystem;
+}
+
 namespace AudioCore {
 namespace HLE {
 
@@ -35,6 +39,9 @@ public:
     /// Resets internal state.
     void Reset();
 
+    /// Sets the memory system to read data from
+    void SetMemory(Memory::MemorySystem& memory);
+
     /**
      * This is called once every audio frame. This performs per-source processing every frame.
      * @param config The new configuration we've got for this Source from the application.
@@ -56,6 +63,7 @@ public:
 
 private:
     const std::size_t source_id;
+    Memory::MemorySystem* memory_system;
     StereoFrame16 current_frame;
 
     using Format = SourceConfiguration::Configuration::Format;