scsi: ufs: update bus vector name used for slow-auto mode

Set the bus vector name used for slow-auto mode to be "MIN".
For each power mode a specific bus vector name should be selected
from UFS DTS node. Slow-auto mode was missing this specification.

Change-Id: I48de8e70823b75ed3bb4eefe7828f841f2e775eb
Signed-off-by: Noa Rubens <noag@codeaurora.org>