table. This is required in order to set obp-control-relinquished
within the PROM, allowing to safely read the OFW translations node.
Without this, f.e. a `ofwdump -ap` triggers a fatal reset error or
worse things on machines based on USIII and beyond.
In theory this should allow to remove touching %tba in cpu_setregs(),
in practice we seem to currently face a chicken and egg problem when
doing so however.
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