[SCSI] isci: performance-fix, shorten default "no outbound task" timeout

"No task timeout timer reduced from 20 to 2 This timer controls how
long the SCU hardware will hold open the TX side of the connection
before sending a DONE.  The timer allows the hardware to attempt to
optimize the DONE/CLOSE behavior to allow for new COMMAND IU to be
posted.  In practice closing the connection quicker is better."

Signed-off-by: Marcin Tomczak <marcin.tomczak@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>