Commit 
65f6f07b added support for the atmel_df_pow2 standalone program
but missed to add a rule to remove it to the "clean" make target.
Signed-off-by: Wolfgang Denk <wd@denx.de>
 
 clean:
        @rm -f $(obj)examples/standalone/82559_eeprom                     \
+              $(obj)examples/standalone/atmel_df_pow2                    \
               $(obj)examples/standalone/eepro100_eeprom                  \
               $(obj)examples/standalone/hello_world                      \
               $(obj)examples/standalone/interrupt                        \