perf: Fix off by one in perf_swevent_init()

The perf_swevent_enabled[] array has PERF_COUNT_SW_MAX elements.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20101024195041.GT5985@bicker>
Signed-off-by: Ingo Molnar <mingo@elte.hu>