nfsd4: use helper for copying filehandles for replay

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
diff --git a/include/linux/nfsd/state.h b/include/linux/nfsd/state.h
index 128298c..b65b2a6 100644
--- a/include/linux/nfsd/state.h
+++ b/include/linux/nfsd/state.h
@@ -168,8 +168,7 @@
 	unsigned int		rp_buflen;
 	char			*rp_buf;
 	unsigned		intrp_allocated;
-	int			rp_openfh_len;
-	char			rp_openfh[NFS4_FHSIZE];
+	struct knfsd_fh		rp_openfh;
 	char			rp_ibuf[NFSD4_REPLAY_ISIZE];
 };