Moved baseband temporary buffers back into class member variables.

Significant performance hit when declaring on stack. C++ wants to initialize std::array or even raw array with element constructors, was resulting in ~7% CPU utilization, for a buffer that was immediately written over anyway.

firmware/baseband/proc_nfm_audio.hpp

@@ -39,6 +39,16 @@ public:
 	void on_message(const Message* const message) override;
 
 private:
+	std::array<complex16_t, 512> dst;
+	const buffer_c16_t dst_buffer {
+		dst.data(),
+		dst.size()
+	};
+	const buffer_s16_t work_audio_buffer {
+		(int16_t*)dst.data(),
+		sizeof(*dst.data()) * dst.size()
+	};
+
 	dsp::decimate::FIRC8xR16x24FS4Decim8 decim_0;
 	dsp::decimate::FIRC16xR16x32Decim8 decim_1;