ppc: Add CFAR, DAR and DSISR to the dictionary of printable registers

ppc: Add CFAR, DAR and DSISR to the dictionary of printable registers

The CFAR, DAR and DSISR registers are currently missing from the
dictionary of registers that may be printed in the QEMU console.
These are interesting registers when debugging.  With this patch,
the following commands work properly:

     (qemu) print $cfar
     (qemu) print $dar
     (qemu) print $dsisr

Signed-off-by: Tom Musta <tommusta@gmail.com>
Reviewed-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>