f2fs: use xattr_prefix to wrap up

Let's use xattr_prefix instead of open code.
No logic changes.
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/xattr.c

@@ -538,7 +538,7 @@ ssize_t f2fs_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 		if (!handler || (handler->list && !handler->list(dentry)))
 			continue;
 
-		prefix = handler->prefix ?: handler->name;
+		prefix = xattr_prefix(handler);
 		prefix_len = strlen(prefix);
 		size = prefix_len + entry->e_name_len + 1;
 		if (buffer) {