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_handler.hpp b/tools/ipmi_handler.hpp
index 9e86f42..144fc22 100644
--- a/tools/ipmi_handler.hpp
+++ b/tools/ipmi_handler.hpp
@@ -2,6 +2,9 @@
 
 #include "ipmi_interface.hpp"
 
+namespace host_tool
+{
+
 class IpmiHandler : public IpmiInterface
 {
   public:
@@ -10,3 +13,5 @@
     std::vector<std::uint8_t>
         sendPacket(const std::vector<std::uint8_t>& data) override;
 };
+
+} // namespace host_tool