f2fs: use xattr_prefix to wrap up

Let's use xattr_prefix instead of open code.
No logic changes.

Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/xattr.c b/fs/f2fs/xattr.c
index 18d5ffb..fa620d3 100644
--- a/fs/f2fs/xattr.c
+++ b/fs/f2fs/xattr.c
@@ -538,7 +538,7 @@
 		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) {