Add a new qc flag ATA_QCFLAG_IO.  This flag gets set for normal IO
commands originating from SCSI midlayer.  This information will be
used by EH to determine transfer speed reconfiguration.
Signed-off-by: NTejun Heo <htejun@gmail.com>
Signed-off-by: NJeff Garzik <jeff@garzik.org>