audio_core/hle: move implementation of RecvDataIsReady

src/audio_core/dsp_interface.h

@@ -40,6 +40,13 @@ public:
      */
     virtual u16 RecvData(u32 register_number) = 0;
 
+    /**
+     * Checks whether data is ready in one of three DSP registers
+     * @param register_number the index of the register to check
+     * @returns true if data is ready
+     */
+    virtual bool RecvDataIsReady(u32 register_number) const = 0;
+
     /**
      * Reads `length` bytes from the DSP pipe identified with `pipe_number`.
      * @note Can read up to the maximum value of a u16 in bytes (65,535).