[U-Boot] netloop: speed up NetLoop

[Ben Warren]

Heiko Schocher wrote:
> NetLoop polls every cycle with getenv some environment variables.
> This is horribly slow, especially when the environment is big.
>
> This patch reads only the environment variables in NetLoop,
> when they were changed.
>
> Also moved the init part of the NetLoop function in a seperate
> function.
>
> Signed-off-by: Heiko Schocher <hs at denx.de>
> ---
>   
<snip>
Applied.

thanks,
Ben