[U-Boot] Xilinx LL temac update

[monstr at monstr.eu]

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