NFSD: Clean up nfs4svc_encode_compoundres()

In today's Linux NFS server implementation, the NFS dispatcher
initializes each XDR result stream, and the NFSv4 .pc_func and
.pc_encode methods all use xdr_stream-based encoding. This keeps
rq_res.len automatically updated. There is no longer a need for
the WARN_ON_ONCE() check in nfs4svc_encode_compoundres().
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfs4xdr.c

@@ -5459,12 +5459,8 @@ bool
 nfs4svc_encode_compoundres(struct svc_rqst *rqstp, struct xdr_stream *xdr)
 {
 	struct nfsd4_compoundres *resp = rqstp->rq_resp;
-	struct xdr_buf *buf = xdr->buf;
 	__be32 *p;
 
-	WARN_ON_ONCE(buf->len != buf->head[0].iov_len + buf->page_len +
-				 buf->tail[0].iov_len);
-
 	/*
 	 * Send buffer space for the following items is reserved
 	 * at the top of nfsd4_proc_compound().