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/S50alsa

@@ -0,0 +1,40 @@
+#!/bin/sh
+#
+# Alsa config
+#
+
+source /etc/profile
+
+start() {
+    printf "Restore alsa"
+    alsactl restore
+    echo "OK"
+}
+
+stop() {
+    printf "Store alsa"
+#   alsactl store
+    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 $?