Suppress implicit-fallthrough warnings in audioflinger etc.

Add FALLTHROUGH_INTENDED for clang compiler.

Bug: 112564944
Test: build with global -Wimplicit-fallthrough.
Change-Id: I8875bc7ed073aae84d5df97eb39c8c745ca627ef
diff --git a/services/audioflinger/Threads.cpp b/services/audioflinger/Threads.cpp
index 4ca50d7..c2320bc 100644
--- a/services/audioflinger/Threads.cpp
+++ b/services/audioflinger/Threads.cpp
@@ -4357,7 +4357,7 @@
                     isActive = false;
                     break;
                 }
-                // fall through
+                FALLTHROUGH_INTENDED;
             case TrackBase::STOPPING_2:
             case TrackBase::PAUSED:
             case TrackBase::STOPPED: