perf, powerpc: Implement group scheduling transactional APIs

[paulus@samba.org: Set cpuhw->event[i]->hw.config in
power_pmu_commit_txn.]

Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20100508102841.GA10650@brick.ozlabs.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>