ufs: add UFS 2.0 to ufshcd-pltfrm bindings

Add UFS 2.0 to the ufshcd-pltfrm devicetree binding.

Signed-off-by: Joao Pinto <jpinto@synopsys.com>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Tomas Winkler <tomas.winkler@intel.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>