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/lpc.cpp b/tools/lpc.cpp
index 9e8e01d..97b7902 100644
--- a/tools/lpc.cpp
+++ b/tools/lpc.cpp
@@ -16,8 +16,13 @@
 
 #include "lpc.hpp"
 
+namespace host_tool
+{
+
 bool LpcDataHandler::sendContents(const std::string& input,
                                   std::uint16_t session)
 {
     return false;
 }
+
+} // namespace host_tool