move implementation to ipmi file

Move the entrance point for the IPMI OEM handling to a separate file and
pass in the handler pointer via binding.

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: I4371ebee1c252ab6e9d8a7ff2389583919ecc996
diff --git a/test/cpld_unittest.cpp b/test/cpld_unittest.cpp
index 12a0444..8b22ff1 100644
--- a/test/cpld_unittest.cpp
+++ b/test/cpld_unittest.cpp
@@ -1,6 +1,6 @@
 #include "cpld.hpp"
 #include "handler_mock.hpp"
-#include "main.hpp"
+#include "ipmi.hpp"
 
 #include <cstdint>
 #include <tuple>