[U-Boot] LL TEMAC V7 refactored

[Stephan Linz]

Back to the discussion from August and November I have refactored the
LL TEMAC driver. Just in version V7 it is ready to next review. Thanks
to Marek and Wolfgang to review V4..6.

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/bundle/rexut/net-ll_temac/