FROMGIT: scsi: core: allow auto suspend override by low-level driver

Rework from previous work by:
Sujit Reddy Thumma <sthumma@codeaurora.org>

Until now the scsi mid-layer forbids runtime suspend till userspace enables
it. This is mainly to quarantine some disks with broken runtime power
management or have high latencies executing suspend resume callbacks. If
the userspace doesn't enable the runtime suspend the underlying hardware
will be always on even when it is not doing any useful work and thus
wasting power.

Some low-level drivers for the controllers can efficiently use runtime
power management to reduce power consumption and improve battery life.
Allow runtime suspend parameters override within the LLD itself instead of
waiting for userspace to control the power management.

Link: https://lore.kernel.org/r/1568649411-5127-2-git-send-email-stanley.chu@mediatek.com


Reviewed-by: Avri Altman <avri.altman@wdc.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Bug: 140620770
(cherry picked from commit c74f8056621738f5be9f5d3d7e0caa927b21aef6
 https://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi.git

 misc)
Change-Id: Ib0b9e8bec307179187a57fe47cb747416da38db2
Signed-off-by: Todd Kjos <tkjos@google.com>