[SCSI] aic79xx: Fixup external device reset

Whenever an external device is resetted we really have to take
care to keep the channel in sync. Just notifying SCSI-ML and retry
is not enough as we have to make sure the SCSI bus is not getting
confused, either.
So whenever we detect an external reset we rewrite the command to
TUR, disable packetized command and notify the internal engine
that an abort has happened. This way we trigger a proper bus
reset sequence and all devices will be renegotiated properly.
Kudos to Justin Gibbs and Luben Tuikov for this idea.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>