x86, perf: P4 PMU -- Get rid of redundant check for array index

The caller already has done such a check.
And it was wrong anyway, it had to be '>=' rather than '>'

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Lin Ming <ming.m.lin@intel.com>
LKML-Reference: <20100508112717.130386882@openvz.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>