scsi: ufs-qcom: disable low power modes and run slow on newer controller

Newer UFS controllers (revision 2) still need to be validated properly
hence disable the low power modes for it until they are validated
thoroughly.
Also run the UFS interface in PWM gear until High Speed Gear operation
is stabililized.

Change-Id: I310b49030d084557f487f3095fc7e1cfa68335e6
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
[cang@codeaurora.org: Resolved trivial merge conflicts]
Signed-off-by: Can Guo <cang@codeaurora.org>