move handler specific method to implementation

Move readNameFromConfig from interface header to implementation header.

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: I97080a691fdcdac25ab29d978054f6e47b18f1c3
diff --git a/handler_impl.hpp b/handler_impl.hpp
index 08452d7..b9946a1 100644
--- a/handler_impl.hpp
+++ b/handler_impl.hpp
@@ -58,5 +58,16 @@
     std::vector<std::tuple<uint32_t, std::string>> _pcie_i2c_map;
 };
 
+/**
+ * Given a type, entity instance, and a configuration, return the name.
+ *
+ * @param[in] type - the entity type
+ * @param[in] instance - the entity instance
+ * @param[in] config - the json object holding the entity mapping
+ * @return the name of the entity from the map
+ */
+std::string readNameFromConfig(const std::string& type, uint8_t instance,
+                               const nlohmann::json& config);
+
 } // namespace ipmi
 } // namespace google