[U-Boot] Add support for imxrt - Sdram

[Fabio Estevam]

Hi Giulio,

On Thu, Oct 10, 2019 at 2:30 PM Giulio Benetti
<giulio.benetti at benettiengineering.com> wrote:
>
> Hi Fabio and Stefano,
>
> about imxrt porting, would it make sense to add an SDRAM driver to setup
> ram or is it enough to provide .cfg file with DCD?

Having the DDR initialization running in C code from internal RAM is
more flexible as you can run SPL, for example.