perf stat: Fix command option / manpage

-l is not supported, it should be -S for scale.

Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <1245703959.6167.16.camel@localhost.localdomain>
Signed-off-by: Ingo Molnar <mingo@elte.hu>