[SCSI] advansys: Remove `done' queue

 - Move the guts of asc_scsi_done_list() into a new function, asc_scsi_done.
 - Call asc_scsi_done() in asc_isr_callback() and adv_isr_callback().  The
   comment was wrong; scsi_done cannot enable interrupts.
 - All other places which queued an scp on the done list are error paths
   for queuecommand, and so we can just call asc_scsi_done() in queuecommand
   if we receive an error.
 - We no longer need to keep a list of done requests in advansys_interrupt

Signed-off-by: Matthew Wilcox <matthew@wil.cx>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>