scsi: dt-bindings: ufs: Add bindings for Cadence UFS

This patch adds a DT binding documentation for Cadence UFS Host Controller.

Signed-off-by: Jan Kotas <jank@cadence.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>