KVM: PPC: Book3S HV: Fix machine check delivery to guest

The code that delivered a machine check to the guest after handling
it in real mode failed to load up r11 before calling kvmppc_msr_interrupt,
which needs the old MSR value in r11 so it can see the transactional
state there.  This adds the missing load.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>