Ok, I just built from my 2013R1-RC1 tree, albeit with my customizations, and get the same error. My hunch is that this indicates the problem is in bf527-ezkit_defconfig not being in sync with recent kernel sources.
My guess is that you can either wait for someone with a BF527 EZ-KIT to tell you what changes they made to get it working, or you can figure out how to make the changes yourself. I'm sure the latter sounds daunting, but that's the nature of open source!