split out handler implementation from interface

Split out the handler object definition from the interface and drop the
default parameters.

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: Ie8c9dbf7881bbe6b5af3596a60430e3b3d573762
diff --git a/eth.hpp b/eth.hpp
index fee363d..4454818 100644
--- a/eth.hpp
+++ b/eth.hpp
@@ -25,8 +25,7 @@
 // Sys can query the ifName and IPMI channel of the BMC's NCSI ethernet
 // device.
 ipmi_ret_t getEthDevice(const uint8_t* reqBuf, uint8_t* replyBuf,
-                        size_t* dataLen,
-                        const HandlerInterface* handler = &handlerImpl);
+                        size_t* dataLen, const HandlerInterface* handler);
 
 } // namespace ipmi
 } // namespace google