hal: retry a2dp path start up when failed

Check if a2dp path start failed and do retry from
out_write to recover the path is possible, which
can avoid blocking write if path set up failed.

Bug: 148926518
Change-Id: I479386e1760b214c1be31d34449a068e41ff5ced
diff --git a/hal/audio_hw.h b/hal/audio_hw.h
index 055a96b..6931d8d 100644
--- a/hal/audio_hw.h
+++ b/hal/audio_hw.h
@@ -739,6 +739,7 @@
     struct listnode audio_patch_record_list;
     Hashmap *patch_map;
     Hashmap *io_streams_map;
+    bool a2dp_started;
     bool ha_proxy_enable;
 };