scsi: ufs-mediatek: enable low-power mode for hibern8 state

In MediaTek Chipsets, UniPro link and ufshci can enter proprietary
low-power mode while link is in hibern8 state.

Link: https://lore.kernel.org/r/20200117035108.19699-4-stanley.chu@mediatek.com


Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Reviewed-by: Asutosh Das <asutoshd@codeaurora.org>
Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>