Ran into this exact problem before some head-against-wall action, and eventually running into this :
https://ko.osdn.jp/projects/uclinux-h8/scm/git/linux/commits/484611e53047b55163822bfe60424a55a31775b3
If you're wondering why i'm building FEC as Module, it's because I need to use RTnet/Xenomai and be able to switchover to the Realtime driver.