Fix trivial print format error.

* Use %zu for size_t values for both 32 and 64-bit modes.

Change-Id: Iee7227211272a45aaed544c7b14130e31c91b349
diff --git a/tests/aidl_test_service.cpp b/tests/aidl_test_service.cpp
index 17c47ee..621694e 100644
--- a/tests/aidl_test_service.cpp
+++ b/tests/aidl_test_service.cpp
@@ -100,7 +100,7 @@
   }
 
   void LogRepeatedStringToken(const String16& token) {
-    ALOGI("Repeating '%s' of length=%u", android::String8(token).string(),
+    ALOGI("Repeating '%s' of length=%zu", android::String8(token).string(),
           token.size());
   }