tools: put all host-side code into host_tool namespace

To avoid confusion and organize the code itself more cleanly, place the
host-side code into its own namespace.

Change-Id: I573eb0494eb59874adb1d1eadc502499e928e396
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/tools/ipmi_interface.hpp b/tools/ipmi_interface.hpp
index 082af9c..8be624c 100644
--- a/tools/ipmi_interface.hpp
+++ b/tools/ipmi_interface.hpp
@@ -3,6 +3,9 @@
 #include <cstdint>
 #include <vector>
 
+namespace host_tool
+{
+
 class IpmiInterface
 {
   public:
@@ -18,3 +21,5 @@
     virtual std::vector<std::uint8_t>
         sendPacket(const std::vector<std::uint8_t>& data) = 0;
 };
+
+} // namespace host_tool