[U-Boot] Xilinx LL temac update

Hi Ben,

I updated LL-temac driver - all fixes are there. Ad to your point Microblaze uses only one ethernet core. It is possible to use a lot of IPs but I don't have board like this to test it that's why I don't want change it.

If you find any other problem please let me know. If is OK - I'll create net branch with these changes (LL_TEMAC/Emaclite + removing old Emac driver)

Thanks, Michal