ieee1394: sbp2: slightly reorder sbp2scsi_abort

Put the target's fetch agent into reset state before the underlying ORB
DMA is unmapped and the ->done handler is called.  It is highly unlikely
but the target could access that ORB right before sbp2 sends the reset
request.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>