arm: Remove old rockchip support

[manu]

Summary

Remove the port for rk30xx.
Kernel config was removed in r346096 and this port was never migrated
to GENERIC.
It is also impossible to obtain such hardware nowadays and this code
don't provide anything beside booting.

[imp]

Do we need to document the removal? Release notes for this are fine unless we specifically document it elsewhere.

[manu]

In D27280#609452, @imp wrote:

Do we need to document the removal? Release notes for this are fine unless we specifically document it elsewhere.

I doubt anyone cares about this code for a long time now so relnote are enough I think.

[imp]

In D27280#609471, @manu wrote:

In D27280#609452, @imp wrote:

Do we need to document the removal? Release notes for this are fine unless we specifically document it elsewhere.

I doubt anyone cares about this code for a long time now so relnote are enough I think.

That was my first read, but I thought it useful to ask the bigger question which might be answered differently for other bits and to help establish norms here that are flexible for the obscure case, but useful when lots of people may be affected. Here the impact seems small enough