We don't emulate breakpoints yet, so just ignore reads and writes
to / from DABR.

This fixes booting of more recent Linux guest kernels for me.
Reported-by: NNello Martuscielli <ppc.addon@gmail.com>
Tested-by: NNello Martuscielli <ppc.addon@gmail.com>
Signed-off-by: NAlexander Graf <agraf@suse.de>