scsi: ufs: Fix up auto hibern8 enablement

Fix up possible unclocked register access to auto hibern8 register in
resume path and through sysfs entry. Meanwhile, enable auto hibern8 only
after device is fully initialized in probe path.

Link: https://lore.kernel.org/r/1573798172-20534-4-git-send-email-cang@codeaurora.org


Reviewed-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Can Guo <cang@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>