aac_read() and aac_write() may complete a command but return -1, which
is propagated through aac_scsi_cmd() to the mid layer through
->queuecommand. If the command has been completed, it must return 0.
Signed-off-by: Jens Axboe <axboe@suse.de>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>