hidl-gen: add LOG_TAG to *All.cpp

This way we can see the package/interface a log message is associated
with.

Test: manually verification
Change-Id: I3fd9487a11b5e6c0692e9fd19c08b082341ec8b9
diff --git a/generateCpp.cpp b/generateCpp.cpp
index fe898c2..45edd44 100644
--- a/generateCpp.cpp
+++ b/generateCpp.cpp
@@ -920,6 +920,10 @@
 
     Formatter out(file);
 
+    out << "#define LOG_TAG \""
+        << mPackage.string() << "::" << baseName
+        << "\"\n\n";
+
     out << "#include <android/log.h>\n";
     out << "#include <cutils/trace.h>\n";
     out << "#include <hidl/HidlTransportSupport.h>\n\n";