Remove exra whitespace from files (#189)

* Remove multiple newlines at the end of files
* Remove the whitespace from the end of lines

net/devif/devif_iobsend.c

@@ -85,4 +85,3 @@ void devif_iob_send(FAR struct net_driver_s *dev, FAR struct iob_s *iob,
 }
 
 #endif /* CONFIG_MM_IOB */
-

net/devif/devif_loopback.c

@@ -159,4 +159,3 @@ int devif_loopback(FAR struct net_driver_s *dev)
 
   return 1;
 }
-