audioflinger: add standby() method to MmapStreamInterface

Bug: 33398120
Test: open/start/stop/close MMAP no IRQ stream for capture and playback

Change-Id: I48ec202a71565f759c441c2a835d8c8190e76334
diff --git a/services/audioflinger/Threads.h b/services/audioflinger/Threads.h
index 0a17a8e..422eeb5 100644
--- a/services/audioflinger/Threads.h
+++ b/services/audioflinger/Threads.h
@@ -1540,6 +1540,7 @@
     status_t getMmapPosition(struct audio_mmap_position *position);
     status_t start(const MmapStreamInterface::Client& client, audio_port_handle_t *handle);
     status_t stop(audio_port_handle_t handle);
+    status_t standby();
 
     // RefBase
     virtual     void        onFirstRef();
@@ -1549,6 +1550,7 @@
 
     virtual     void        threadLoop_exit();
     virtual     void        threadLoop_standby();
+    virtual     bool        shouldStandby_l() { return false; }
 
     virtual     status_t    initCheck() const { return (mHalStream == 0) ? NO_INIT : NO_ERROR; }
     virtual     size_t      frameCount() const { return mFrameCount; }