perf report: Add hypervisor dso

Add a dso for hypervisor samples. We don't get any symbol
information on the ppc64 hypervisor but this at least gives
us a high level summary of the time spent in there.

Signed-off-by: Anton Blanchard <anton@samba.org>
Cc: a.p.zijlstra@chello.nl
Cc: paulus@samba.org
LKML-Reference: <20090630230141.182536873@samba.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>