[U-Boot] Disable features

[Derek Ou]

Wolfgang Denk wrote:
> Why would compiled in Network support slow down the boot process?
>
> The network interface will only be initialized as soon as you use it.
> If you don't have one, then you probably will not try using it - then
> why would it delay your boot?
>   
When we have the Network support compiled, it takes a few second to do 
the auto-negotiation
even though MAC chip is not on board.  Then it fails out and goes to 
autoboot.  Is it a
board specific problem or system problem?

Thanks,
Derek