9P: fix return value in v9fs_fid_xattr_set

v9fs_fid_xattr_set is supposed to return 0 on success.

This corrects the behaviour introduced in commit
bdd5c28dcb8330b9074404cc92a0b83aae5606a
"9p: fix return value in case in v9fs_fid_xattr_set()"

(The function returns a negative error on error, as expected)

Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
diff --git a/fs/9p/xattr.c b/fs/9p/xattr.c
index 04133a1..f95e01e 100644
--- a/fs/9p/xattr.c
+++ b/fs/9p/xattr.c
@@ -156,7 +156,7 @@
 		offset += write_count;
 		value_len -= write_count;
 	}
-	retval = offset;
+	retval = 0;
 err:
 	p9_client_clunk(fid);
 	return retval;