[PATCH] libata: add ATA_QCFLAG_IO

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: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>