feat: audio stack working — pulseaudio + x6200_control + voice_rec

- Add pulseaudio in system mode
- Add alsactl restore with correct mixer state from Aether
- Add x6200-control package (I2C hardware control library)
- Audio chain: pulseaudio -> x6200_control_init -> voice_rec -> speaker

br2_external/board/x6200/rootfs-overlay/etc/init.d/S50pulseaudio

@@ -0,0 +1,45 @@
+#!/bin/sh
+#
+# Starts pulseaudio.
+#
+
+
+start() {
+	printf "Starting pulseaudio: "
+	umask 007
+	/usr/bin/pulseaudio \
+		--system \
+		--daemonize \
+		--disallow-exit \
+		--exit-idle-time=-1 \
+		--use-pid-file \
+		--disable-shm
+	echo "OK"
+}
+stop() {
+	printf "Stopping pulseaudio: "
+	PULSE_RUNTIME_PATH=/var/run/pulse /usr/bin/pulseaudio --kill
+	echo "OK"
+}
+restart() {
+	stop
+	start
+}
+
+case "$1" in
+  start)
+	start
+	;;
+  stop)
+	stop
+	;;
+  restart|reload)
+	restart
+	;;
+  *)
+	echo "Usage: $0 {start|stop|restart}"
+	exit 1
+esac
+
+exit $?
+