NFSv4.1/pnfs: Ensure layoutreturn reserves space for the opaque payload

The "FIXME" is outdated. Flexfiles does add a payload.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index a7be571..ff4784c 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -400,7 +400,8 @@
 #define decode_layoutcommit_maxsz (op_decode_hdr_maxsz + 3)
 #define encode_layoutreturn_maxsz (8 + op_encode_hdr_maxsz + \
 				encode_stateid_maxsz + \
-				1 /* FIXME: opaque lrf_body always empty at the moment */)
+				1 + \
+				XDR_QUADLEN(NFS4_OPAQUE_LIMIT))
 #define decode_layoutreturn_maxsz (op_decode_hdr_maxsz + \
 				1 + decode_stateid_maxsz)
 #define encode_secinfo_no_name_maxsz (op_encode_hdr_maxsz + 1)