scsi: ufs: Fix possible unclocked access to auto hibern8 timer register

Before access auto hibner8 timer register, make sure power and clock are
properly configured to avoid unclocked register access.

Link: https://lore.kernel.org/r/1583398391-14273-1-git-send-email-cang@codeaurora.org
Fixes: ba7af5ec

 ("scsi: ufs: export ufshcd_auto_hibern8_update for vendor usage")
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>