dt-bindings: display: xlnx: Add support for DP Tx SS v3.1

commit f89de4bfd77bad87fcb015c367c66c737fa72010 from
https://github.com/Xilinx/linux-xlnx.git

 xlnx_rebase_v5.15

VTC sub-core offset is now changed in DP Tx SS and IP Version has been
updated to 3.1. This patch adds support for DP Tx SS v3.1

Signed-off-by: Rajesh Gugulothu <rajesh.gugulothu@amd.com>
Reviewed-by: Vishal Sagar <vishal.sagar@amd.com>
State: pending
Signed-off-by: Quanyang Wang <quanyang.wang@windriver.com>