Correct typos in perf bench & perf sched help text.

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <20100331113100.cc898487.randy.dunlap@oracle.com>
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>