[U-Boot] at91: fix a USB problem for AT91SAM9261

[Remy Bohmer]

Hi,

>> In that case the description is wrong. It states:
>> > the USB support for all AT91SAM9261 based boards doesn't work.
>> Look at the word 'ALL', that mislead me here...
> ok I've not tick on the all
>
> why not replace with
> the USB support for all AT91SAM9261 based boards will only work if the PLLB
> will be configured by a precedent bootloader.

OK

Remy