drm/tidss: Add support for AM625 DSS

Add support for the DSS IP on TI's new AM625 SoC in the tidss driver.

Signed-off-by: Aradhya Bhatia <a-bhatia1@ti.com>
Reviewed-by: Rahul T R <r-ravikumar@ti.com>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>