scsi: ufs-mediatek: customize the delay for enabling host

scsi: ufs-mediatek: customize the delay for enabling host

MediaTek platform and UFS controller can dynamically customize the delay
for host enabling according to different scenarios.

For example, if UniPro enters lower-power mode, such delay can be
minimized, otherwise longer delay shall be expected.

Link: https://lore.kernel.org/r/20200318104016.28049-8-stanley.chu@mediatek.com
Reviewed-by: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>