perf_event_init() wants to start using IDR trees, its needs in turn
are satisfied by mm_init().
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20101117222056.206992649@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>