[SCSI] sd: implement START/STOP management

[SCSI] sd: implement START/STOP management

Implement SBC START/STOP management.  sdev->mange_start_stop is added.
When it's set to one, sd STOPs the device on suspend and shutdown and
STARTs it on resume.  sdev->manage_start_stop defaults is in sdev
instead of scsi_disk cdev to allow ->slave_config() override the
default configuration but is exported under scsi_disk sysfs node as
sdev->allow_restart is.

When manage_start_stop is zero (the default value), this patch doesn't
introduce any behavior change.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Rejections fixed and
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>