Enable ddr modes on emmc2 of Raspberry Pi 4 B

[Tobias Schramm]

Hi Stefan,

> Can you please explain why this sd-uhs-ddr50 property is necessary?
> 
> From my testings with a UHS SD card the UHS DDR50 mode is already
> properly configured before your patch.

I must have been high on something while testing. I've just checked
again and the sd-uhs-ddr50 property is indeed not required. Thanks for
correcting me there. I'll send a v2 without that property set.


Best Regards,

Tobias