NFSD: Reorder the fields in struct nfsd4_op

Pack the fields to reduce the size of struct nfsd4_op, which is used
an array in struct nfsd4_compoundargs.

sizeof(struct nfsd4_op):
Before: /* size: 672, cachelines: 11, members: 5 */
After:  /* size: 640, cachelines: 10, members: 5 */
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/xdr4.h

@@ -606,8 +606,9 @@ struct nfsd4_copy_notify {
 
 struct nfsd4_op {
 	u32					opnum;
-	const struct nfsd4_operation *		opdesc;
 	__be32					status;
+	const struct nfsd4_operation		*opdesc;
+	struct nfs4_replay			*replay;
 	union nfsd4_op_u {
 		struct nfsd4_access		access;
 		struct nfsd4_close		close;
@@ -671,7 +672,6 @@ struct nfsd4_op {
 		struct nfsd4_listxattrs		listxattrs;
 		struct nfsd4_removexattr	removexattr;
 	} u;
-	struct nfs4_replay *			replay;
 };
 
 bool nfsd4_cache_this_op(struct nfsd4_op *);