PatchPanel: Specify latency units for patches

When the latency number is too high, it becomes ambiguous
whether it's in milli- or nano-seconds.

Test: dumpsys
Change-Id: I175a562f403dc4d67e50687927cd4edf9bc7d922
diff --git a/services/audioflinger/PatchPanel.cpp b/services/audioflinger/PatchPanel.cpp
index 7b165a1..538a0eb 100644
--- a/services/audioflinger/PatchPanel.cpp
+++ b/services/audioflinger/PatchPanel.cpp
@@ -598,7 +598,7 @@
     // add latency if it exists
     double latencyMs;
     if (getLatencyMs(&latencyMs) == OK) {
-        result.appendFormat("  latency: %.2lf", latencyMs);
+        result.appendFormat("  latency: %.2lf ms", latencyMs);
     }
     return result;
 }