[PATCH] rk3399: Add basic support for helios64

[Christian Glombek]

I've looked into this a bit over the weekend - my current WIP patch can be
found here:
https://src.fedoraproject.org/fork/lorbus/rpms/uboot-tools/blob/helios64/f/0001-arm-Add-support-for-Kobol-Helios64-board.patch

It's essentially the entire devicetree used in Armbian, only that I had to
remove the gpio{1,2,4} initialization since `gpio-hog` doesn't appear to
work with upstream u-boot.
It boots fine with current Fedora IoT 34 nightlies, but kernel crashes are
very regular (sometimes recoverable, sometimes not), which looks to me like
the same problem that Armbian builds have, logs seem to point to an issue
with the dmc frequency.
I've compiled an excerpt of interesting looking logs from a couple of boots
here (you should be able to comment on the doc as well):
https://hackmd.io/@lorbus/SyXTj0lXu

Please take a look and let me know what you think.

Best regards,
Christian