scsi: ufs: kick start clock scaling only after device detection

UFS clock scaling might start kicking in even before the device
is running at the fastest interface speed which is undesirable.
This change moves the clock scaling kick start only after the
device is detected and running at the fastest interface speed.

Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>