Hide warning in cutils/trace.h

system/core/include is included in the global include path using
-isystem, which hides all warnings.  cutils/trace.h has an ignored
return value warning, move the implementation to trace-dev.c so it
doesn't cause warnings in every module that includes it in preparation
for moving from -isystem to -I.

Test: m -j native
Bug: 31492149
Change-Id: If8b3fe13059c9e59c2d5208294d427d84fa6e588
diff --git a/include/cutils/trace.h b/include/cutils/trace.h
index c9790ad..dc3833f 100644
--- a/include/cutils/trace.h
+++ b/include/cutils/trace.h
@@ -188,8 +188,8 @@
 static inline void atrace_end(uint64_t tag)
 {
     if (CC_UNLIKELY(atrace_is_tag_enabled(tag))) {
-        char c = 'E';
-        write(atrace_marker_fd, &c, 1);
+        void atrace_end_body();
+        atrace_end_body();
     }
 }