README: Note this layer is not for the MinnowBoard MAX
README: Note this layer is not for the MinnowBoard MAX

This is only for the original MinnowBoard, make this very obvious in the
README and provide a link to the right documentation.

Signed-off-by: Darren Hart <38f9eaa30910c40b06f5a60020b1222f2a953801@infradead.org>

koenkooi/meta-minnow,koenkooi/meta-minnow