Make put_padding() have a consistent argument order.

Thanks to Alex Landau for pointing out that commit 8b98fea4a
introduced two uses of it with the arguments one way round and one
with them the other way round. (Plus a fourth use where it doesn't
matter, because the padding at the end of the encrypted blob of an
OpenSSH PEM private key consists of n bytes with value n. :-)

On the basis of majority vote, I've switched the order in the function
definition to match the two of the three call sites that expressed the
same opinion, and fixed the third.

ssh2bpp.c

@@ -582,7 +582,7 @@ static void ssh2_bpp_format_packet(BinaryPacketProtocol *bpp, PktOut *pkt)
                                       s->out.sequence);
     }
 
-    put_padding(pkt, 0, maclen);
+    put_padding(pkt, maclen, 0);
 
     if (s->out.mac && s->out.etm_mode) {
         /*