Add back an interface used by an external provider

The move to the new API removed the ipmid_get_sdbus_plus_handler
interface because it looked like it was self-contained in the
executable, not realizing it was needed by an external provider.

Change-Id: I75bb898294cc59cae7d291f7a6a6ed1e61d62903
Signed-off-by: Vernon Mauery <vernon.mauery@linux.intel.com>
diff --git a/include/ipmid-host/cmd.hpp b/include/ipmid-host/cmd.hpp
index e46c485..ca73bd2 100644
--- a/include/ipmid-host/cmd.hpp
+++ b/include/ipmid-host/cmd.hpp
@@ -1,6 +1,8 @@
 #include <ipmid-host/cmd-utils.hpp>
 #include <memory>
-#include <sdbusplus/bus.hpp>
+#include <sdbusplus/asio/connection.hpp>
 
 // Global Host Bound Command manager
 extern void ipmid_send_cmd_to_host(phosphor::host::command::CommandHandler&&);
+extern std::unique_ptr<sdbusplus::asio::connection>&
+    ipmid_get_sdbus_plus_handler();