scsi: ufs: add UFS HS-G4 support

New generation (3.0) UFS devices are capable of running at HS-G4
(High Speed Gear 4) which is 2x faster than previous generation
UFS devices. This change adds all required support to make our host
controller work with these faster devices.

Change-Id: I3efc6ce6ab1e90bca78348518a1f50d8d5be971e
Signed-off-by: Bao D. Nguyen <nguyenb@codeaurora.org>
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>