[U-Boot] LL TEMAC V4 refactored

Back to the discussion from August I have refactored the LL TEMAC driver. Just in version V4 it is ready to next review.

Note: To use the driver on Microblaze, you will need additional platform patches by Michal Simek: - http://patchwork.ozlabs.org/patch/112535/ - http://patchwork.ozlabs.org/patch/112534/ - http://patchwork.ozlabs.org/patch/112532/

I will collect all related patches on a public bundle: - http://patchwork.ozlabs.org/user/bundle/2339/

br, Stephan Linz