scsi: ufs: ufs-mediatek: ensure UniPro is not powered down before linkup

scsi: ufs: ufs-mediatek: ensure UniPro is not powered down before linkup

MediaTek Chipsets can enter proprietary UniPro low-power mode during
suspend while link is in hibern8 state. Make sure leaving low-power mode
before every link startup to prevent lockup in any possible error recovery
path.

At the same time, re-factor related funcitons to improve code readability.

Link: https://lore.kernel.org/r/20200129105251.12466-2-stanley.chu@mediatek.com
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Reviewed-by: Bean Huo <beanhuo@micron.com>
Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>