mx5: Fix CONFIG_OF_LIBFDT redefined warning

With the following commit, CONFIG_OF_LIBFDT is redefined.

  2fa8ca98c37d5b1bb0328b19ddb7e9d162cd9683
  Add CONFIG_OF_LIBFDT to more boards.

Remove the duplicated definition to fix CONFIG_OF_LIBFDT redefined
warning.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
2 files changed