Merge branch 'rxrpc-ack-fixes'

David Howells says:

====================
rxrpc: ACK handling fixes

Here are a couple of patches to fix ACK handling in AF_RXRPC:

 (1) Allow RTT determination to use an ACK of any type as the response from
     which to calculate RTT, provided ack.serial matches the serial number
     of the outgoing packet.

 (2) Defer the response to a PING ACK packet (or any ACK with the
     REQUEST_ACK flag set) until after we've parsed the packet so that we
     carry up to date information if the Tx or Rx rings are advanced.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>