Start audio DMA only in apps that use audio (#1982)

* Start audio DMA only in apps that use audio
* Rename main.cpp to main.cpp.unuse
* shrink_tx_buffer fix for transfers_per_buffer==1 scenario

firmware/baseband/proc_tones.cpp

@@ -23,6 +23,7 @@
 #include "proc_tones.hpp"
 #include "sine_table_int8.hpp"
 #include "event_m4.hpp"
+#include "audio_dma.hpp"
 
 #include <cstdint>
 
@@ -154,6 +155,8 @@ void TonesProcessor::on_message(const Message* const p) {
 }
 
 int main() {
+    audio::dma::init_audio_out();
+
     EventDispatcher event_dispatcher{std::make_unique<TonesProcessor>()};
     event_dispatcher.run();
     return 0;