pNFS/flexfiles: missing error code in ff_layout_alloc_lseg()

If xdr_inline_decode() fails then we end up returning ERR_PTR(0).  The
caller treats NULL returns as -ENOMEM so it doesn't really hurt runtime,
but obviously we intended to set an error code here.

Fixes: d67ae825 ("pnfs/flexfiles: Add the FlexFile Layout Driver")
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/flexfilelayout/flexfilelayout.c

@@ -454,6 +454,7 @@ ff_layout_alloc_lseg(struct pnfs_layout_hdr *lh,
 			goto out_err_free;
 
 		/* fh */
+		rc = -EIO;
 		p = xdr_inline_decode(&stream, 4);
 		if (!p)
 			goto out_err_free;