perf tests: Fix compile failure on do_sort_something

Commit b55ae0a9 added code-reading.c which fails to compile on Fedora 16
with compiler version:
$ gcc --version
gcc (GCC) 4.6.3 20120306 (Red Hat 4.6.3-2)

Failure message is:

tests/code-reading.c: In function ‘do_sort_something’:
tests/code-reading.c:305:13: error: stack protector not protecting local variables: variable length buffer [-Werror=stack-protector]
cc1: all warnings being treated as errors
make: *** [/tmp/junk/tests/code-reading.o] Error 1
make: *** Waiting for unfinished jobs....

v2: as Adrian noticed changed sizeof to ARRAY_SIZE

Signed-off-by: David Ahern <dsahern@gmail.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1376454732-83728-1-git-send-email-dsahern@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/tests/code-reading.c

@@ -304,15 +304,14 @@ static int comp(const void *a, const void *b)
 
 static void do_sort_something(void)
 {
-	size_t sz = 40960;
-	int buf[sz], i;
+	int buf[40960], i;
 
-	for (i = 0; i < (int)sz; i++)
-		buf[i] = sz - i - 1;
+	for (i = 0; i < (int)ARRAY_SIZE(buf); i++)
+		buf[i] = ARRAY_SIZE(buf) - i - 1;
 
-	qsort(buf, sz, sizeof(int), comp);
+	qsort(buf, ARRAY_SIZE(buf), sizeof(int), comp);
 
-	for (i = 0; i < (int)sz; i++) {
+	for (i = 0; i < (int)ARRAY_SIZE(buf); i++) {
 		if (buf[i] != i) {
 			pr_debug("qsort failed\n");
 			break;