Fix a typo in Javadoc comment.

src/main/java/net/floodlightcontroller/util/MACAddress.java

@@ -16,7 +16,7 @@ public class MACAddress {
     }
 
     /**
-     * Reteruns a MAC address instance representing the value of the specified {@code String}.
+     * Returns a MAC address instance representing the value of the specified {@code String}.
      * @param address the String representation of the MAC Address to be parsed.
      * @return a MAC Address instance representing the value of the specified {@code String}.
      * @throws IllegalArgumentException if the string cannot be parsed as a MAC address.