PPC: mac newworld: fix cpu NIP reset value

PPC: mac newworld: fix cpu NIP reset value

On -M mac99, we can run 970 CPUs. However, these CPUs define the initial
instruction pointer they start execution at as part of their bootup protocol,
so effectively it's up to the board to decide where they start.

This went unnoticed, because they used to boot at the same location our flash
was mapped to, but due to the recent reset changes our 970 CPUs want to reset
to 0x100 now, which is always a 0 instruction.

Set the initial IP to something reasonable for -M mac99.

Signed-off-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Fabien Chouteau <chouteau@adacore.com>