9pfs: fix v9fs_mark_fids_unreclaim() return value

The return value of v9fs_mark_fids_unreclaim() is then propagated to
pdu_complete(). It should be a negative errno, not -1.
Signed-off-by: NGreg Kurz <groug@kaod.org>
Reviewed-by: NEric Blake <eblake@redhat.com>

hw/9pfs/9p.c

@@ -512,7 +512,7 @@ static int coroutine_fn v9fs_mark_fids_unreclaim(V9fsPDU *pdu, V9fsPath *path)
             /* reopen the file/dir if already closed */
             err = v9fs_reopen_fid(pdu, fidp);
             if (err < 0) {
-                return -1;
+                return err;
             }
             /*
              * Go back to head of fid list because