perf tests: Fix compile failure on do_sort_something

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 <[email protected]>
Acked-by: Adrian Hunter <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Jiri Olsa <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>