rxrpc: Show stats counter for received reason-0 ACKs

In /proc/net/rxrpc/stats, show the stats counter for received ACKs that
have the reason code set to 0 as some implementations do this.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Link: https://patch.msgid.link/20241204074710.990092-7-dhowells@redhat.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>