IDE error recovery is using IDLE IMMEDIATE if the drive is busy or has DRQ set.
This violates the ATA spec (can only send IDLE IMMEDIATE when drive is not
busy) and really hoses up some drives (modern drives will not be able to
recover using this error handling).  The correct thing to do is issue a SRST
followed by a SET FEATURES command.  This is what Western Digital recommends
for error recovery and what Western Digital says Windows does.  It also does
not violate the ATA spec as far as I can tell.

Bart:
* port the patch over the current tree
* undo the recalibration code removal
* send SET FEATURES command after checking for good drive status
* don't check whether the current request is of REQ_TYPE_ATA_{CMD,TASK}
  type because we need to send SET FEATURES before handling any requests
* some pre-ATA4 drives require INITIALIZE DEVICE PARAMETERS command before
  other commands (except IDENTIFY) so send SET FEATURES only if there are
  no pending drive->special requests
* update comments and patch description
* any bugs introduced by this patch are mine and not Suleiman's :-)
Signed-off-by: Suleiman Souhlal <suleiman@google.com>
Acked-by: Alan Cox <alan@redhat.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>