Remove a common subexpression from profman output

Change-Id: I12fa4a36f4e9d980a720bb52c6b736ffc91a6700
(cherry picked from commit 727074b62ef86dfb631a99214e6726d7d9c6c6be)
diff --git a/profman/profman.cc b/profman/profman.cc
index b3454fa..37a560d 100644
--- a/profman/profman.cc
+++ b/profman/profman.cc
@@ -219,7 +219,7 @@
     static constexpr uint64_t kLogThresholdTime = MsToNs(100);  // 100ms
     uint64_t time_taken = NanoTime() - start_ns_;
     if (time_taken > kLogThresholdTime) {
-      LOG(WARNING) << "profman took " << PrettyDuration(NanoTime() - start_ns_);
+      LOG(WARNING) << "profman took " << PrettyDuration(time_taken);
     }
   }