[OE-core] [PATCH] mkefidisk.sh: add deprecation warning to the output

[Randy Witt]

>>> We should also document, the wic steps in wiki pages e.g. http://wiki.minnowboard.org/Yocto_Project
>> It's already documented in README.hardware: https://git.yoctoproject.org/cgit/cgit.cgi/poky/tree/README.hardware
>>
>> And in Yocto manual:
>> http://www.yoctoproject.org/docs/2.2/mega-manual/mega-manual.html#building-an-image-for-hardware
>
> Thanks, now can you also nudge the minnowboard.org to do the same ?
>

Pinging you John. :)

>>
>> --
>> Regards,
>> Ed
>>