configure: libnpp is always nonfree, even with LGPL

libnpp was erroneously grouped up with libfdk-aac and openssl to check
if --enable-nonfree wasn't passed only with --enable-gpl in
9f28db47accb31bfec40a56dd2dc19ffd366a6be. The latter two are compatible
with LGPL, libnpp is not.

Signed-off-by: James Almer <jamrial@gmail.com>
