sources: Fix ifdefs

We don't want to compare the boolean value of these macros, but the
existence of their definition. None of our Makefile definitions define
an actual value for them, but rely on their presence.

Change-Id: I21688d70acfbfef4d8ca3284fd6db8dbf64b7e6f
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/ethernet_interface.cpp b/ethernet_interface.cpp
index 607e658..2de60e4 100644
--- a/ethernet_interface.cpp
+++ b/ethernet_interface.cpp
@@ -122,7 +122,7 @@
     EthernetInterfaceIntf::linkUp(linkUp());
     EthernetInterfaceIntf::nicEnabled(nicEnabled());
 
-#if NIC_SUPPORTS_ETHTOOL
+#ifdef NIC_SUPPORTS_ETHTOOL
     InterfaceInfo ifInfo = EthernetInterface::getInterfaceInfo();
 
     EthernetInterfaceIntf::autoNeg(std::get<2>(ifInfo));
@@ -348,7 +348,7 @@
     return objectPath;
 }
 
-#if NIC_SUPPORTS_ETHTOOL
+#ifdef NIC_SUPPORTS_ETHTOOL
 /*
   Enable this code if your NIC driver supports the ETHTOOL features.
   Do this by adding the following to your phosphor-network*.bbappend file.