perf cgroup: Fix a typo in kernel config

s/specificied/specified

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <4D6F348C.2050804@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>