[nnpkg/tflite_run] make help option work (#6879)

[nnpkg/tflite_run] make help option work (#6879)

Currently, tflite/nnpackage_run does not recognize help option.

It complains like:

$ LD_LIBRARY_PATH=Product/out/lib Product/out/bin/nnpackage_run --help
terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::program_options::required_option> >'
  what():  the option '--nnpackage' is required but missing
  Aborted (core dumped)

This patch fixes it by notifying errors after parsing help option.

Signed-off-by: Sanggyu Lee <sg5.lee@samsung.com>