scsi: docs: ABI: sysfs-driver-ufs: Add DeepSleep power mode

Update sysfs documentation for addition of DeepSleep power mode.

Link: https://lore.kernel.org/r/20210104155026.16417-1-adrian.hunter@intel.com


Fixes: fe1d4c2e ("scsi: ufs: Add DeepSleep feature")
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>