[U-Boot] fw_env bug for multi-sector environments on NOR flash

[Fei, Yiyang]

Dear Mr. Denk,

> Stupid question: why do you define an environment size of 128 kB?
> I bet you use less than 10% of this, right?

Correct

> Are you aware that this has a lof of disadvantages, lile
> significantly slowing down your boot process?

I am now, but the first product is already released and cannot be
changed easily.

> Your Signed-off-by: line is missing...

I resubmitted updated message.

Best regards,
Yiyang Fei