perf stat: Fix tool option consistency: rename -S/--scale to -c/--scale

We want to use a coherent flag for -S/--stat across all tools,
so free up -S in perf stat.

Signed-off-by: Brice Goglin <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: [e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

tools/perf/Documentation/perf-stat.txt

···
 -a::
         system-wide collection
 
--S::
+-c::
         scale counter values
 
 EXAMPLES

tools/perf/builtin-stat.c

···
 		    "stat events on existing pid"),
 	OPT_BOOLEAN('a', "all-cpus", &system_wide,
 		    "system-wide collection from all CPUs"),
-	OPT_BOOLEAN('S', "scale", &scale,
+	OPT_BOOLEAN('c', "scale", &scale,
 		    "scale/normalize counters"),
 	OPT_BOOLEAN('v', "verbose", &verbose,
 		    "be more verbose (show counter open errors, etc)"),