NFSD: Use xdr_pad_size()

Clean up: Use a helper instead of open-coding the calculation of
the XDR pad size.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfs4xdr.c

@@ -3940,9 +3940,8 @@ static __be32 nfsd4_encode_readv(struct nfsd4_compoundres *resp,
 {
 	struct xdr_stream *xdr = resp->xdr;
 	unsigned int starting_len = xdr->buf->len;
+	__be32 zero = xdr_zero;
 	__be32 nfserr;
-	__be32 tmp;
-	int pad;
 
 	read->rd_vlen = xdr_reserve_space_vec(xdr, resp->rqstp->rq_vec, maxcount);
 	if (read->rd_vlen < 0)
@@ -3958,11 +3957,9 @@ static __be32 nfsd4_encode_readv(struct nfsd4_compoundres *resp,
 		return nfserr_io;
 	xdr_truncate_encode(xdr, starting_len + xdr_align_size(maxcount));
 
-	tmp = xdr_zero;
-	pad = (maxcount&3) ? 4 - (maxcount&3) : 0;
-	write_bytes_to_xdr_buf(xdr->buf, starting_len + maxcount, &tmp, pad);
-	return 0;
-
+	write_bytes_to_xdr_buf(xdr->buf, starting_len + maxcount, &zero,
+			       xdr_pad_size(maxcount));
+	return nfs_ok;
 }
 
 static __be32