fio: build warning fix on gcc-3.4.6-3

fio: build warning fix on  gcc-3.4.6-3

On gcc-3.4.6-3

 >make log.o
gcc -W -Wwrite-strings -Wall -D_GNU_SOURCE -D_LARGEFILE_SOURCE
-D_FILE_OFFSET_BITS=64 -O2 -g  -D_FORTIFY_SOURCE=2 -rdynamic  -c -o
log.o log.c
log.c: In function `read_iolog':
log.c:308: warning: int format, fio_ddir arg (arg 3)

Which corresponds to

enum fio_ddir rw;
..
..
if (sscanf(p, "%d,%llu,%u", &rw, &offset, &bytes) != 3) {

Following patch will fix the warning. This was added by commit
21bd2987dc5d82a18af485cd1e7841e94137fc0c

Thanks,
-Guru

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>