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.cpp b/tools/ipmi_handler.cpp
index 76bd3e0..a0c1198 100644
--- a/tools/ipmi_handler.cpp
+++ b/tools/ipmi_handler.cpp
@@ -16,8 +16,13 @@
 
 #include "ipmi_handler.hpp"
 
+namespace host_tool
+{
+
 std::vector<std::uint8_t>
     IpmiHandler::sendPacket(const std::vector<std::uint8_t>& data)
 {
     return {};
 }
+
+} // namespace host_tool