drm/amd/display: Use DPM table clk setting for dml2 soc dscclk

[WHY]
Not like dppclk/dispclk, dml2 will calculate the minimum required clocks.
For dscclk, it is used for pure comparision.

Reviewed-by: Alvin Lee <alvin.lee2@amd.com>
Signed-off-by: Charlene Liu <Charlene.Liu@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>