[PATCH] Enable support for PPC64 on qemu target

[Alexander Graf]

This patch enables OpenBIOS to initialize on PPC64, enabling support  
for -cpu 970fx.
It gets up to the boot prompt and works rather good so far, though I  
haven't been able to run a kernel yet.

For more recent PowerPC CPUs the PTE layout has changed, so we need to  
take that into account and create PTEs according to the new layout and  
at the new physical positions.

Signed-off-by: Alexander Graf