sensors/zones: place in namespace and cleanup

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: I527dbc8477a232945f696227a7b0b2adbee45175
diff --git a/sensors/buildjson.cpp b/sensors/buildjson.cpp
index 7e5e29a..2bfc143 100644
--- a/sensors/buildjson.cpp
+++ b/sensors/buildjson.cpp
@@ -25,6 +25,8 @@
 
 using json = nlohmann::json;
 
+namespace pid_control
+{
 namespace conf
 {
 void from_json(const json& j, conf::SensorConfig& s)
@@ -113,3 +115,4 @@
 
     return config;
 }
+} // namespace pid_control