coccicheck complains about the use of snprintf() in sysfs show functions.
Fix the following coccicheck warning:
fs/f2fs/sysfs.c:198:12-20: WARNING: use scnprintf or sprintf.
fs/f2fs/sysfs.c:247:8-16: WARNING: use scnprintf or sprintf.
Use sysfs_emit instead of scnprintf or sprintf makes more sense.
Signed-off-by: Qing Wang <wangqing@xxxxxxxx>