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: I863e2c24fbbbe4be4f93e2e78641c06c0951f6fd
Signed-off-by: Bao D. Nguyen <nguyenb@codeaurora.org>