drm/amd/display: Program dpp dto based on actual dpp clk

[Why]
dpp dto phase and modulo are programmed with actual dpp global clk
and pipe clk. Need to use actual dpp clk to prgoram dpp dto modulo
to get more accuracy ratio.

[How]
assign actual dpp clk to dccg for dpp modulo programming.

Signed-off-by: Yongqiang Sun <yongqiang.sun@amd.com>
Acked-by: Bindu Ramamurthy <bindu.r@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>