scsi: ufs: add load based scaling of UFS gear

UFS driver's load based clock scaling feature scales down the ufs related
clocks in order to allow low power modes of chipsets. UniPro 1.6 supports
maximum gear up to HS-G3 (High Speed Gear3) and some of the chipsets
low power modes may not be allowed in HS-G3 hence this change adds support
to scale gear between HS-G3 and HS-G1 based on same existing load based
clock scaling logic.

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