sensors/zones: place in namespace and cleanup

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: I527dbc8477a232945f696227a7b0b2adbee45175
diff --git a/sensors/host.hpp b/sensors/host.hpp
index 7983e8a..35c7f45 100644
--- a/sensors/host.hpp
+++ b/sensors/host.hpp
@@ -16,6 +16,9 @@
 using ValueInterface = sdbusplus::xyz::openbmc_project::Sensor::server::Value;
 using ValueObject = ServerObject<ValueInterface>;
 
+namespace pid_control
+{
+
 class ValueHelper : public ValueInterface
 {
 
@@ -62,3 +65,5 @@
     std::chrono::high_resolution_clock::time_point _updated;
     double _value = 0;
 };
+
+} // namespace pid_control