pass the relative data offset of data in/out pdu's to the scsi data in/out dissector...

pass the relative data offset of data in/out pdu's to the scsi data in/out dissector (dissect_scsi_payload) so that we can later add reassembly of data pdu's
and also (if reassembly is disabled) only dissect the initial (offset==0) data pdu.

dissect_scsi_payload() does not yet use this parameter.

now that we have both data offset and expected data length/bidir expected data length and also the read/write flags availabe we have what we need to reassemble data in/out pdus    (modulo overflow/underflow  but those are so rare we can worry about them later).

ndmp:   ndmp conceptually always has a data in and a data out phase and never fragment the data into smaller pdu's os that dissector always report offset as 0.

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@19511 f5534014-38df-0310-8fa8-9805f1628bb7