You can't boot a kdump kernel via OF, not reliably anyway, the kernel being at
32 MB conflicts with the zImage wrapper etc. and it blows up.

It's trivial to check in prom_init though, and this is early enough that we can
actually drop back to OF where a reset-all will get you going again, which is
kinda nice. I think this should go in for 2.6.16.
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>