perf tools: Use ARRAY_SIZE() instead of ad hoc equivalent, spotted by array_size.cocci

Fix the following coccicheck warning:

tools/perf/util/trace-event-parse.c:209:35-36: WARNING: Use ARRAY_SIZE

ARRAY_SIZE(arr) is a macro provided in tools/include/linux/kernel.h,
which not only measures the size of the array, but also makes sure
that `arr` is really an array.

It has been tested with gcc (Debian 8.3.0-6) 8.3.0.

Signed-off-by: Guo Zhengkui <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: http://lore.kernel.org/lkml/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/trace-event-parse.c

···
 	if (isdigit(flag[0]))
 		return strtoull(flag, NULL, 0);
 
-	for (i = 0; i < (int)(sizeof(flags)/sizeof(flags[0])); i++)
+	for (i = 0; i < (int)(ARRAY_SIZE(flags)); i++)
 		if (strcmp(flags[i].name, flag) == 0)
 			return flags[i].value;