Add support for rock3b board

[JDuchniewicz]

Adds support for Radxa Rock3b board. Based on the implementation of rockpro64 board.

[Indanz]

I just realised you copied the current rockpro64 timer driver, and probably the serial driver too I guess (haven't checked).

Please don't do that, just adapt the current drivers so it's suitable for both boards and use a symlink here to make it compile.

[Indanz]

Getting in the right direction, but still unnecessary code duplication remaining.

[Indanz]

Please tidy up the commit history a bit.

Once that's done and the copyright mess is fixed, it's good to go.

[JDuchniewicz]

@Indanz is there anything else I should do to get this merged? I see some failures in the HW runs but I fail to understand why they are happening (my code did not touch these platforms at all).

[Indanz]

@Indanz is there anything else I should do to get this merged?

I don't think so. Just bring seL4 up-to-date so I can merge it I think. @lsf37, do you have anything?

I see some failures in the HW runs but I fail to understand why they are happening (my code did not touch these platforms at all).

They're unrelated. Our CI system is not the most stable at the moment, not sure what's going on, people messing around in the server room or whatever.

[lsf37]

All good to go from my side. The remaining zcu106 failure is the known flakiness of that particular board in the machine queue.