scsi: ufs: host: mediatek: Disable auto-hibern8 during power mode changes

Disable auto-hibern8 during power mode transitions to prevent unintended
entry into auto-hibern8. Restore the original auto-hibern8 timer value
after completing the power mode change to maintain system stability and
prevent potential issues during power state transitions.

Signed-off-by: Peter Wang <peter.wang@mediatek.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>