f2fs: replace snprintf in show functions with sysfs_emit

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@vivo.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/sysfs.c

@@ -196,7 +196,7 @@ static ssize_t encoding_show(struct f2fs_attr *a,
 	struct super_block *sb = sbi->sb;
 
 	if (f2fs_sb_has_casefold(sbi))
-		return snprintf(buf, PAGE_SIZE, "%s (%d.%d.%d)\n",
+		return sysfs_emit(buf, "%s (%d.%d.%d)\n",
 			sb->s_encoding->charset,
 			(sb->s_encoding->version >> 16) & 0xff,
 			(sb->s_encoding->version >> 8) & 0xff,
@@ -245,7 +245,7 @@ static ssize_t avg_vblocks_show(struct f2fs_attr *a,
 static ssize_t main_blkaddr_show(struct f2fs_attr *a,
 				struct f2fs_sb_info *sbi, char *buf)
 {
-	return snprintf(buf, PAGE_SIZE, "%llu\n",
+	return sysfs_emit(buf, "%llu\n",
 			(unsigned long long)MAIN_BLKADDR(sbi));
 }