nfsd4: move more write parameters into xdr argument

In preparation for moving some of this elsewhere.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/xdr4.h

@@ -386,6 +386,8 @@ struct nfsd4_write {
 	u32		wr_stable_how;      /* request */
 	u32		wr_buflen;          /* request */
 	int		wr_vlen;
+	struct kvec	wr_head;
+	struct page **	wr_pagelist;        /* request */
 
 	u32		wr_bytes_written;   /* response */
 	u32		wr_how_written;     /* response */