sensors/zones: place in namespace and cleanup

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: I527dbc8477a232945f696227a7b0b2adbee45175
diff --git a/sensors/host.cpp b/sensors/host.cpp
index 96a0514..e05ac37 100644
--- a/sensors/host.cpp
+++ b/sensors/host.cpp
@@ -21,6 +21,9 @@
 #include <memory>
 #include <mutex>
 
+namespace pid_control
+{
+
 template <typename T>
 void scaleHelper(T& ptr, int64_t value)
 {
@@ -92,3 +95,5 @@
 {
     throw std::runtime_error("Not Implemented.");
 }
+
+} // namespace pid_control