[U-Boot] MAKEALL build error on usb/master branch

[Marek Vasut]

Dear Troy Kisky,

> Hi Marek
> 
> I thought you might like to be aware of this error, if not already known.

Known, when building for MXS (mx23 and mx28), you need libssl-dev installed 
(openssl development libs and headers). Same rule applies when you use signed 
FIT images.

So, solution is to install libssl-dev (for debian-based distro) or whatever your 
favorite distro has.

Best regards,
Marek Vasut